===================================================================
RCS file: /cvs/mandoc/mandoc_char.7,v
retrieving revision 1.14
retrieving revision 1.78
diff -u -p -r1.14 -r1.78
--- mandoc/mandoc_char.7	2009/09/22 10:07:01	1.14
+++ mandoc/mandoc_char.7	2020/10/31 11:45:16	1.78
@@ -1,6 +1,8 @@
-.\"	$Id: mandoc_char.7,v 1.14 2009/09/22 10:07:01 kristaps Exp $
+.\"	$Id: mandoc_char.7,v 1.78 2020/10/31 11:45:16 schwarze Exp $
 .\"
-.\" Copyright (c) 2009 Kristaps Dzonsons <kristaps@kth.se>
+.\" Copyright (c) 2003 Jason McIntyre <jmc@openbsd.org>
+.\" Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
+.\" Copyright (c) 2011,2013,2015,2017-2020 Ingo Schwarze <schwarze@openbsd.org>
 .\"
 .\" Permission to use, copy, modify, and distribute this software for any
 .\" purpose with or without fee is hereby granted, provided that the above
@@ -13,34 +15,239 @@
 .\" WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
 .\" ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
 .\" OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
-.\" 
-.Dd $Mdocdate: September 22 2009 $
+.\"
+.Dd $Mdocdate: October 31 2020 $
 .Dt MANDOC_CHAR 7
 .Os
-.\" SECTION
 .Sh NAME
 .Nm mandoc_char
 .Nd mandoc special characters
-.\" SECTION
 .Sh DESCRIPTION
-This documents the special characters and predefined strings accepted by 
+This page documents the
+.Xr roff 7
+escape sequences accepted by
 .Xr mandoc 1
-to format
+to represent special characters in
 .Xr mdoc 7
 and
 .Xr man 7
-documents.  Specific output devices of
-.Xr mandoc 1 ,
-dictated by the
-.Fl T Ns Ar output
-argument, will properly render these sequences.
-.\" PARAGRAPH
+documents.
 .Pp
-Both
-.Xr mdoc 7
+The rendering depends on the
+.Xr mandoc 1
+output mode; it can be inspected by calling
+.Xr man 1
+on the
+.Nm
+manual page with different
+.Fl T
+arguments.
+In ASCII output, the rendering of some characters may be hard
+to interpret for the reader.
+Many are rendered as descriptive strings like
+.Qq <integral> ,
+.Qq <degree> ,
+or
+.Qq <Gamma> ,
+which may look ugly, and many are replaced by similar ASCII characters.
+In particular, accented characters are usually shown without the accent.
+For that reason, try to avoid using any of the special characters
+documented here except those discussed in the
+.Sx DESCRIPTION ,
+unless they are essential for explaining the subject matter at hand,
+for example when documenting complicated mathematical functions.
+.Pp
+In particular, in English manual pages, do not use special-character
+escape sequences to represent national language characters in author
+names; instead, provide ASCII transcriptions of the names.
+.Ss Dashes and Hyphens
+In typography there are different types of dashes of various width:
+the hyphen (\(hy),
+the en-dash (\(en),
+the em-dash (\(em),
+and the mathematical minus sign (\(mi).
+.Pp
+Hyphens are used for adjectives;
+to separate the two parts of a compound word;
+or to separate a word across two successive lines of text.
+The hyphen does not need to be escaped:
+.Bd -unfilled -offset indent
+blue-eyed
+lorry-driver
+.Ed
+.Pp
+The en-dash is used to separate the two elements of a range,
+or can be used the same way as an em-dash.
+It should be written as
+.Sq \e(en :
+.Bd -unfilled -offset indent
+pp. 95\e(en97.
+Go away \e(en or else!
+.Ed
+.Pp
+The em-dash can be used to show an interruption
+or can be used the same way as colons, semi-colons, or parentheses.
+It should be written as
+.Sq \e(em :
+.Bd -unfilled -offset indent
+Three things \e(em apples, oranges, and bananas.
+This is not that \e(em rather, this is that.
+.Ed
+.Pp
+In
+.Xr roff 7
+documents, the minus sign is normally written as
+.Sq \e- .
+In manual pages, some style guides recommend to also use
+.Sq \e-
+if an ASCII 0x2d
+.Dq hyphen-minus
+output glyph that can be copied and pasted is desired in output modes
+supporting it, for example in
+.Fl T Cm utf8
 and
-.Xr man 7
-encode special characters with 
+.Fl T Cm html .
+But currently, no practically relevant manual page formatter requires
+that subtlety, so in manual pages, it is sufficient to write plain
+.Sq -
+to represent hyphen, minus, and hyphen-minus.
+.Pp
+If a word on a text input line contains a hyphen, a formatter may decide
+to insert an output line break after the hyphen if that helps filling
+the current output line, but the whole word would overflow the line.
+If it is important that the word is not broken across lines in this
+way, a zero-width space
+.Pq Sq \e&
+can be inserted before or after the hyphen.
+While
+.Xr mandoc 1
+never breaks the output line after hyphens adjacent to a zero-width
+space, after any of the other dash- or hyphen-like characters
+represented by escape sequences, or after hyphens inside words in
+macro arguments, other software may not respect these rules and may
+break the line even in such cases.
+.Pp
+Some
+.Xr roff 7
+implementations contains dictionaries allowing to break the line
+at syllable boundaries even inside words that contain no hyphens.
+Such automatic hyphenation is not supported by
+.Xr mandoc 1 ,
+which only breaks the line at whitespace, and inside words only
+after existing hyphens.
+.Ss Spaces
+To separate words in normal text, for indenting and alignment
+in literal context, and when none of the following special cases apply,
+just use the normal space character
+.Pq Sq \  .
+.Pp
+When filling text, output lines may be broken between words, i.e. at space
+characters.
+To prevent a line break between two particular words,
+use the unpaddable non-breaking space escape sequence
+.Pq Sq \e\ \&
+instead of the normal space character.
+For example, the input string
+.Dq number\e\ 1
+will be kept together as
+.Dq number\ 1
+on the same output line.
+.Pp
+On request and macro lines, the normal space character serves as an
+argument delimiter.
+To include whitespace into arguments, quoting is usually the best choice;
+see the MACRO SYNTAX section in
+.Xr roff 7 .
+In some cases, using the non-breaking space escape sequence
+.Pq Sq \e\ \&
+may be preferable.
+.Pp
+To escape macro names and to protect whitespace at the end
+of input lines, the zero-width space
+.Pq Sq \e&
+is often useful.
+For example, in
+.Xr mdoc 7 ,
+a normal space character can be displayed in single quotes in either
+of the following ways:
+.Pp
+.Dl .Sq \(dq \(dq
+.Dl .Sq \e \e&
+.Ss Quotes
+On request and macro lines, the double-quote character
+.Pq Sq \(dq
+is handled specially to allow quoting.
+One way to prevent this special handling is by using the
+.Sq \e(dq
+escape sequence.
+.Pp
+Note that on text lines, literal double-quote characters can be used
+verbatim.
+All other quote-like characters can be used verbatim as well,
+even on request and macro lines.
+.Ss Accents
+In output modes supporting such special output characters, for example
+.Fl T Cm pdf ,
+and sometimes less consistently in
+.Fl T Cm utf8 ,
+some
+.Xr roff 7
+formatters convert the following ASCII input characters to the
+following Unicode special output characters:
+.Bl -column x(ga U+2018 -offset indent
+.It \(ga Ta U+2018 Ta left single quotation mark
+.It \(aq Ta U+2019 Ta right single quotation mark
+.It \(ti Ta U+02DC Ta small tilde
+.It \(ha Ta U+02C6 Ta modifier letter circumflex
+.El
+.Pp
+In prose, this automatic substitution is often desirable;
+but when these characters have to be displayed as plain ASCII
+characters, for example in source code samples, they require
+escaping to render as follows:
+.Bl -column x(ga U+2018 -offset indent
+.It \e(ga Ta U+0060 Ta grave accent
+.It \e(aq Ta U+0027 Ta apostrophe
+.It \e(ti Ta U+007E Ta tilde
+.It \e(ha Ta U+005E Ta circumflex accent
+.El
+.Ss Periods
+The period
+.Pq Sq \&.
+is handled specially at the beginning of an input line,
+where it introduces a
+.Xr roff 7
+request or a macro, and when appearing alone as a macro argument in
+.Xr mdoc 7 .
+In such situations, prepend a zero-width space
+.Pq Sq \e&.
+to make it behave like normal text.
+.Pp
+Do not use the
+.Sq \e.
+escape sequence.
+It does not prevent special handling of the period.
+.Ss Backslashes
+To include a literal backslash
+.Pq Sq \e
+into the output, use the
+.Pq Sq \ee
+escape sequence.
+.Pp
+Note that doubling it
+.Pq Sq \e\e
+is not the right way to output a backslash.
+Because
+.Xr mandoc 1
+does not implement full
+.Xr roff 7
+functionality, it may work with
+.Xr mandoc 1 ,
+but it may have weird effects on complete
+.Xr roff 7
+implementations.
+.Sh SPECIAL CHARACTERS
+Special characters are encoded as
 .Sq \eX
 .Pq for a one-character escape ,
 .Sq \e(XX
@@ -48,626 +255,575 @@ encode special characters with 
 and
 .Sq \e[N]
 .Pq N-character .
-One may generalise
-.Sq \e(XX
-as
-.Sq \e[XX]
-and
-.Sq \eX
-as
-.Sq \e[X] .
-Predefined strings are functionally similar to special characters, using 
-.Sq \e*X
-.Pq for a one-character escape ,
-.Sq \e*(XX
-.Pq two-character ,
-and
-.Sq \e*[N]
-.Pq N-character .
-One may generalise
-.Sq \e*(XX
-as
-.Sq \e*[XX]
-and
-.Sq \e*X
-as
-.Sq \e*[X] .
-.\" SECTION
-.Sh Special Characters
-These are the preferred input symbols for producing special characters.
-.\" PARAGRAPH
+For details, see the
+.Em Special Characters
+subsection of the
+.Xr roff 7
+manual.
 .Pp
-Typographic:
-.Bl -tag -width Ds -offset indent -compact
-.It \e~
-.Pq non-breaking space
-.It \e
-.Pq space
-.It \e^
-.Pq zero-width space
-.It \e%
-.Pq zero-width space
-.It \e&
-.Pq zero-width space
-.It \e|
-.Pq zero-width space
+Spaces, non-breaking unless stated otherwise:
+.Bl -column "Input" "Description" -offset indent -compact
+.It Em Input Ta Em Description
+.It Sq \e\ \& Ta unpaddable space
+.It \e\(ti   Ta paddable space
+.It \e0      Ta digit-width space
+.It \e|      Ta one-sixth \e(em narrow space, zero width in nroff mode
+.It \e^      Ta one-twelfth \e(em half-narrow space, zero width in nroff
+.It \e&      Ta zero-width space
+.It \e)      Ta zero-width space transparent to end-of-sentence detection
+.It \e%      Ta zero-width space allowing hyphenation
+.It \e:      Ta zero-width space allowing line break
 .El
-.\" PARAGRAPH
 .Pp
-Grammatic:
-.Bl -tag -width Ds -offset indent -compact
-.It \e(em
-.Pq em-dash
-.It \e(en
-.Pq en-dash
-.It \e(hy
-.Pq hyphen
-.It \e\e
-.Pq back-slash
-.It \\e
-.Pq back-slash
-.It \e'
-.Pq apostrophe
-.It \e`
-.Pq back-tick
-.It \e.
-.Pq period
-.It \e(r!
-.Pq upside-down exclamation
-.It \e(r?
-.Pq upside-down question
+Lines:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(ba    Ta \(ba        Ta bar
+.It \e(br    Ta \(br        Ta box rule
+.It \e(ul    Ta \(ul        Ta underscore
+.It \e(ru    Ta \(ru        Ta underscore (width 0.5m)
+.It \e(rn    Ta \(rn        Ta overline
+.It \e(bb    Ta \(bb        Ta broken bar
+.It \e(sl    Ta \(sl        Ta forward slash
+.It \e(rs    Ta \(rs        Ta backward slash
 .El
-.\" PARAGRAPH
 .Pp
-Enclosures:
-.Bl -tag -width Ds -offset indent -compact
-.It \e(lh
-.Pq left hand
-.It \e(rh
-.Pq right hand
-.It \e(Fo
-.Pq left guillemet
-.It \e(Fc
-.Pq right guillemet
-.It \e(fo
-.Pq left guilsing
-.It \e(fc
-.Pq right guilsing
-.It \e(rC
-.Pq right brace
-.It \e(lC
-.Pq left brace
-.It \e(ra
-.Pq right angle
-.It \e(la
-.Pq left angle
-.It \e(rB
-.Pq right bracket
-.It \e(lB
-.Pq left bracket
-.It \e(lq
-.Pq left double-quote
-.It \e(rq
-.Pq right double-quote
-.It \e(oq
-.Pq left single-quote
-.It \e(aq
-.Pq right single-quote
-.It \e(Bq
-.Pq right low double-quote
-.It \e(bq
-.Pq right low single-quote
+Text markers:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(ci    Ta \(ci        Ta circle
+.It \e(bu    Ta \(bu        Ta bullet
+.It \e(dd    Ta \(dd        Ta double dagger
+.It \e(dg    Ta \(dg        Ta dagger
+.It \e(lz    Ta \(lz        Ta lozenge
+.It \e(sq    Ta \(sq        Ta white square
+.It \e(ps    Ta \(ps        Ta paragraph
+.It \e(sc    Ta \(sc        Ta section
+.It \e(lh    Ta \(lh        Ta left hand
+.It \e(rh    Ta \(rh        Ta right hand
+.It \e(at    Ta \(at        Ta at
+.It \e(sh    Ta \(sh        Ta hash (pound)
+.It \e(CR    Ta \(CR        Ta carriage return
+.It \e(OK    Ta \(OK        Ta check mark
+.It \e(CL    Ta \(CL        Ta club suit
+.It \e(SP    Ta \(SP        Ta spade suit
+.It \e(HE    Ta \(HE        Ta heart suit
+.It \e(DI    Ta \(DI        Ta diamond suit
 .El
-.\" PARAGRAPH
 .Pp
-Indicatives:
-.Bl -tag -width Ds -offset indent -compact
-.It \e(<-
-.Pq left arrow
-.It \e(->
-.Pq right arrow
-.It \e(ua
-.Pq up arrow
-.It \e(da
-.Pq down arrow
-.It \e(<>
-.Pq left-right arrow
-.It \e(lA
-.Pq left double-arrow
-.It \e(rA
-.Pq right double-arrow
-.It \e(uA
-.Pq up double-arrow
-.It \e(dA
-.Pq down double-arrow
-.It \e(hA
-.Pq left-right double-arrow
+Legal symbols:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(co    Ta \(co        Ta copyright
+.It \e(rg    Ta \(rg        Ta registered
+.It \e(tm    Ta \(tm        Ta trademarked
 .El
-.\" PARAGRAPH
 .Pp
+Punctuation:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(em    Ta \(em        Ta em-dash
+.It \e(en    Ta \(en        Ta en-dash
+.It \e(hy    Ta \(hy        Ta hyphen
+.It \ee      Ta \e          Ta back-slash
+.It \e.      Ta \.          Ta period
+.It \e(r!    Ta \(r!        Ta upside-down exclamation
+.It \e(r?    Ta \(r?        Ta upside-down question
+.El
+.Pp
+Quotes:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(Bq    Ta \(Bq        Ta right low double-quote
+.It \e(bq    Ta \(bq        Ta right low single-quote
+.It \e(lq    Ta \(lq        Ta left double-quote
+.It \e(rq    Ta \(rq        Ta right double-quote
+.It \e(oq    Ta \(oq        Ta left single-quote
+.It \e(cq    Ta \(cq        Ta right single-quote
+.It \e(aq    Ta \(aq        Ta apostrophe quote (ASCII character)
+.It \e(dq    Ta \(dq        Ta double quote (ASCII character)
+.It \e(Fo    Ta \(Fo        Ta left guillemet
+.It \e(Fc    Ta \(Fc        Ta right guillemet
+.It \e(fo    Ta \(fo        Ta left single guillemet
+.It \e(fc    Ta \(fc        Ta right single guillemet
+.El
+.Pp
+Brackets:
+.Bl -column "xxbracketrightbtx" Rendered Description -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(lB    Ta \(lB        Ta left bracket
+.It \e(rB    Ta \(rB        Ta right bracket
+.It \e(lC    Ta \(lC        Ta left brace
+.It \e(rC    Ta \(rC        Ta right brace
+.It \e(la    Ta \(la        Ta left angle
+.It \e(ra    Ta \(ra        Ta right angle
+.It \e(bv    Ta \(bv        Ta brace extension (special font)
+.It \e[braceex] Ta \[braceex] Ta brace extension
+.It \e[bracketlefttp] Ta \[bracketlefttp] Ta top-left hooked bracket
+.It \e[bracketleftbt] Ta \[bracketleftbt] Ta bottom-left hooked bracket
+.It \e[bracketleftex] Ta \[bracketleftex] Ta left hooked bracket extension
+.It \e[bracketrighttp] Ta \[bracketrighttp] Ta top-right hooked bracket
+.It \e[bracketrightbt] Ta \[bracketrightbt] Ta bottom-right hooked bracket
+.It \e[bracketrightex] Ta \[bracketrightex] Ta right hooked bracket extension
+.It \e(lt    Ta \(lt        Ta top-left hooked brace
+.It \e[bracelefttp] Ta \[bracelefttp] Ta top-left hooked brace
+.It \e(lk    Ta \(lk        Ta mid-left hooked brace
+.It \e[braceleftmid] Ta \[braceleftmid] Ta mid-left hooked brace
+.It \e(lb    Ta \(lb        Ta bottom-left hooked brace
+.It \e[braceleftbt] Ta \[braceleftbt] Ta bottom-left hooked brace
+.It \e[braceleftex] Ta \[braceleftex] Ta left hooked brace extension
+.It \e(rt    Ta \(rt        Ta top-left hooked brace
+.It \e[bracerighttp] Ta \[bracerighttp] Ta top-right hooked brace
+.It \e(rk    Ta \(rk        Ta mid-right hooked brace
+.It \e[bracerightmid] Ta \[bracerightmid] Ta mid-right hooked brace
+.It \e(rb    Ta \(rb        Ta bottom-right hooked brace
+.It \e[bracerightbt] Ta \[bracerightbt] Ta bottom-right hooked brace
+.It \e[bracerightex] Ta \[bracerightex] Ta right hooked brace extension
+.It \e[parenlefttp] Ta \[parenlefttp] Ta top-left hooked parenthesis
+.It \e[parenleftbt] Ta \[parenleftbt] Ta bottom-left hooked parenthesis
+.It \e[parenleftex] Ta \[parenleftex] Ta left hooked parenthesis extension
+.It \e[parenrighttp] Ta \[parenrighttp] Ta top-right hooked parenthesis
+.It \e[parenrightbt] Ta \[parenrightbt] Ta bottom-right hooked parenthesis
+.It \e[parenrightex] Ta \[parenrightex] Ta right hooked parenthesis extension
+.El
+.Pp
+Arrows:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(<-    Ta \(<-        Ta left arrow
+.It \e(->    Ta \(->        Ta right arrow
+.It \e(<>    Ta \(<>        Ta left-right arrow
+.It \e(da    Ta \(da        Ta down arrow
+.It \e(ua    Ta \(ua        Ta up arrow
+.It \e(va    Ta \(va        Ta up-down arrow
+.It \e(lA    Ta \(lA        Ta left double-arrow
+.It \e(rA    Ta \(rA        Ta right double-arrow
+.It \e(hA    Ta \(hA        Ta left-right double-arrow
+.It \e(uA    Ta \(uA        Ta up double-arrow
+.It \e(dA    Ta \(dA        Ta down double-arrow
+.It \e(vA    Ta \(vA        Ta up-down double-arrow
+.It \e(an    Ta \(an        Ta horizontal arrow extension
+.El
+.Pp
+Logical:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(AN    Ta \(AN        Ta logical and
+.It \e(OR    Ta \(OR        Ta logical or
+.It \e[tno]  Ta \[tno]      Ta logical not (text font)
+.It \e(no    Ta \(no        Ta logical not (special font)
+.It \e(te    Ta \(te        Ta existential quantifier
+.It \e(fa    Ta \(fa        Ta universal quantifier
+.It \e(st    Ta \(st        Ta such that
+.It \e(tf    Ta \(tf        Ta therefore
+.It \e(3d    Ta \(3d        Ta therefore
+.It \e(or    Ta \(or        Ta bitwise or
+.El
+.Pp
 Mathematical:
-.Bl -tag -width Ds -offset indent -compact
-.It \e(es
-.Pq empty set
-.It \e(ca
-.Pq intersection
-.It \e(cu
-.Pq union
-.It \e(gr
-.Pq gradient
-.It \e(pd
-.Pq partial differential
-.It \e(ap
-.Pq similarity
-.It \e(sp
-.Pq proper superset
-.It \e(sb
-.Pq proper subset
-.It \e(eq
-.Pq equals
-.It \e(di
-.Pq division
-.It \e(mu
-.Pq multiplication
-.It \e(pl
-.Pq addition
-.It \e-
-.Pq subtraction
-.It \e(nm
-.Pq not element
-.It \e(mo
-.Pq element
-.It \e(Im
-.Pq imaginary
-.It \e(Re
-.Pq real
-.It \e(Ah
-.Pq aleph
-.It \e(te
-.Pq existential quantifier
-.It \e(fa
-.Pq universal quantifier
-.It \e(AN
-.Pq logical AND
-.It \e(OR
-.Pq logical OR
-.It \e(no
-.Pq logical NOT
-.It \e(st
-.Pq such that
-.It \e(tf
-.Pq therefore
-.It \e(~~
-.Pq approximate
-.It \e(~=
-.Pq approximately equals
-.It \e(=~
-.Pq congruent
-.It \e(<=
-.Pq less-than-equal
-.It \e(>=
-.Pq greater-than-equal
-.It \e(==
-.Pq equal
-.It \e(!=
-.Pq not equal
-.It \e(if
-.Pq infinity
-.It \e(na
-.Pq NaN, an extension
-.It \e(+-
-.Pq plus-minus
-.It \e(**
-.Pq asterisk
+.Bl -column "xxcoproductxx" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e-      Ta \-          Ta minus (text font)
+.It \e(mi    Ta \(mi        Ta minus (special font)
+.It +        Ta +           Ta plus (text font)
+.It \e(pl    Ta \(pl        Ta plus (special font)
+.It \e(-+    Ta \(-+        Ta minus-plus
+.It \e[t+-]  Ta \[t+-]      Ta plus-minus (text font)
+.It \e(+-    Ta \(+-        Ta plus-minus (special font)
+.It \e(pc    Ta \(pc        Ta center-dot
+.It \e[tmu]  Ta \[tmu]      Ta multiply (text font)
+.It \e(mu    Ta \(mu        Ta multiply (special font)
+.It \e(c*    Ta \(c*        Ta circle-multiply
+.It \e(c+    Ta \(c+        Ta circle-plus
+.It \e[tdi]  Ta \[tdi]      Ta divide (text font)
+.It \e(di    Ta \(di        Ta divide (special font)
+.It \e(f/    Ta \(f/        Ta fraction
+.It \e(**    Ta \(**        Ta asterisk
+.It \e(<=    Ta \(<=        Ta less-than-equal
+.It \e(>=    Ta \(>=        Ta greater-than-equal
+.It \e(<<    Ta \(<<        Ta much less
+.It \e(>>    Ta \(>>        Ta much greater
+.It \e(eq    Ta \(eq        Ta equal
+.It \e(!=    Ta \(!=        Ta not equal
+.It \e(==    Ta \(==        Ta equivalent
+.It \e(ne    Ta \(ne        Ta not equivalent
+.It \e(ap    Ta \(ap        Ta tilde operator
+.It \e(|=    Ta \(|=        Ta asymptotically equal
+.It \e(=\(ti Ta \(=~        Ta approximately equal
+.It \e(\(ti\(ti Ta \(~~        Ta almost equal
+.It \e(\(ti= Ta \(~=        Ta almost equal
+.It \e(pt    Ta \(pt        Ta proportionate
+.It \e(es    Ta \(es        Ta empty set
+.It \e(mo    Ta \(mo        Ta element
+.It \e(nm    Ta \(nm        Ta not element
+.It \e(sb    Ta \(sb        Ta proper subset
+.It \e(nb    Ta \(nb        Ta not subset
+.It \e(sp    Ta \(sp        Ta proper superset
+.It \e(nc    Ta \(nc        Ta not superset
+.It \e(ib    Ta \(ib        Ta reflexive subset
+.It \e(ip    Ta \(ip        Ta reflexive superset
+.It \e(ca    Ta \(ca        Ta intersection
+.It \e(cu    Ta \(cu        Ta union
+.It \e(/_    Ta \(/_        Ta angle
+.It \e(pp    Ta \(pp        Ta perpendicular
+.It \e(is    Ta \(is        Ta integral
+.It \e[integral] Ta \[integral] Ta integral
+.It \e[sum]    Ta \[sum]   Ta summation
+.It \e[product] Ta \[product] Ta product
+.It \e[coproduct] Ta \[coproduct] Ta coproduct
+.It \e(gr    Ta \(gr        Ta gradient
+.It \e(sr    Ta \(sr        Ta square root
+.It \e[sqrt] Ta \[sqrt]     Ta square root
+.It \e(lc    Ta \(lc        Ta left-ceiling
+.It \e(rc    Ta \(rc        Ta right-ceiling
+.It \e(lf    Ta \(lf        Ta left-floor
+.It \e(rf    Ta \(rf        Ta right-floor
+.It \e(if    Ta \(if        Ta infinity
+.It \e(Ah    Ta \(Ah        Ta aleph
+.It \e(Im    Ta \(Im        Ta imaginary
+.It \e(Re    Ta \(Re        Ta real
+.It \e(wp    Ta \(wp        Ta Weierstrass p
+.It \e(pd    Ta \(pd        Ta partial differential
+.It \e(-h    Ta \(-h        Ta Planck constant over 2\(*p
+.It \e[hbar] Ta \[hbar]     Ta Planck constant over 2\(*p
+.It \e(12    Ta \(12        Ta one-half
+.It \e(14    Ta \(14        Ta one-fourth
+.It \e(34    Ta \(34        Ta three-fourths
+.It \e(18    Ta \(18        Ta one-eighth
+.It \e(38    Ta \(38        Ta three-eighths
+.It \e(58    Ta \(58        Ta five-eighths
+.It \e(78    Ta \(78        Ta seven-eighths
+.It \e(S1    Ta \(S1        Ta superscript 1
+.It \e(S2    Ta \(S2        Ta superscript 2
+.It \e(S3    Ta \(S3        Ta superscript 3
 .El
-.\" PARAGRAPH
 .Pp
 Ligatures:
-.Bl -tag -width Ds -offset indent -compact
-.It \e(ss
-.Pq German eszett
-.It \e(AE
-.Pq AE
-.It \e(ae
-.Pq ae
-.It \e(OE
-.Pq OE
-.It \e(oe
-.Pq oe
-.It \e(ff
-.Pq ff ligature
-.It \e(fi
-.Pq fi ligature
-.It \e(fl
-.Pq fl ligature
-.It \e(Fi
-.Pq ffi ligature
-.It \e(Fl
-.Pq ffl ligature
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(ff    Ta \(ff        Ta ff ligature
+.It \e(fi    Ta \(fi        Ta fi ligature
+.It \e(fl    Ta \(fl        Ta fl ligature
+.It \e(Fi    Ta \(Fi        Ta ffi ligature
+.It \e(Fl    Ta \(Fl        Ta ffl ligature
+.It \e(AE    Ta \(AE        Ta AE
+.It \e(ae    Ta \(ae        Ta ae
+.It \e(OE    Ta \(OE        Ta OE
+.It \e(oe    Ta \(oe        Ta oe
+.It \e(ss    Ta \(ss        Ta German eszett
+.It \e(IJ    Ta \(IJ        Ta IJ ligature
+.It \e(ij    Ta \(ij        Ta ij ligature
 .El
-.\" PARAGRAPH
 .Pp
-Diacritics and accented letters:
-.Bl -tag -width Ds -offset indent -compact
-.It \e(ga
-.Pq grave accent
-.It \e(aa
-.Pq accute accent
-.It \e(a"
-.Pq umlaut accent
-.It \e(ad
-.Pq dieresis accent
-.It \e(a~
-.Pq tilde accent
-.It \e(a^
-.Pq circumflex accent
-.It \e(ac
-.Pq cedilla accent
-.It \e(ad
-.Pq dieresis accent
-.It \e(ah
-.Pq caron accent
-.It \e(ao
-.Pq ring accent
-.It \e(ho
-.Pq hook accent
-.It \e(ab
-.Pq breve accent
-.It \e(a-
-.Pq macron accent
-.It \e(-D
-.Pq Eth
-.It \e(Sd
-.Pq eth
-.It \e(TP
-.Pq Thorn
-.It \e(Tp
-.Pq thorn
-.It \e('A
-.Pq acute A
-.It \e('E
-.Pq acute E
-.It \e('I
-.Pq acute I
-.It \e('O
-.Pq acute O
-.It \e('U
-.Pq acute U
-.It \e('a
-.Pq acute a
-.It \e('e
-.Pq acute e
-.It \e('i
-.Pq acute i
-.It \e('o
-.Pq acute o
-.It \e('u
-.Pq acute u
-.It \e(`A
-.Pq grave A
-.It \e(`E
-.Pq grave E
-.It \e(`I
-.Pq grave I
-.It \e(`O
-.Pq grave O
-.It \e(`U
-.Pq grave U
-.It \e(`a
-.Pq grave a
-.It \e(`e
-.Pq grave e
-.It \e(`i
-.Pq grave i
-.It \e(`o
-.Pq grave o
-.It \e(`u
-.Pq grave u
-.It \e(~A
-.Pq tilde A
-.It \e(~N
-.Pq tilde N
-.It \e(~O
-.Pq tilde O
-.It \e(~a
-.Pq tilde a
-.It \e(~n
-.Pq tilde n
-.It \e(~o
-.Pq tilde o
-.It \e(:A
-.Pq dieresis A
-.It \e(:E
-.Pq dieresis E
-.It \e(:I
-.Pq dieresis I
-.It \e(:O
-.Pq dieresis O
-.It \e(:U
-.Pq dieresis U
-.It \e(:a
-.Pq dieresis a
-.It \e(:e
-.Pq dieresis e
-.It \e(:i
-.Pq dieresis i
-.It \e(:o
-.Pq dieresis o
-.It \e(:u
-.Pq dieresis u
-.It \e(:y
-.Pq dieresis y
-.It \e(^A
-.Pq circumflex A
-.It \e(^E
-.Pq circumflex E
-.It \e(^I
-.Pq circumflex I
-.It \e(^O
-.Pq circumflex O
-.It \e(^U
-.Pq circumflex U
-.It \e(^a
-.Pq circumflex a
-.It \e(^e
-.Pq circumflex e
-.It \e(^i
-.Pq circumflex i
-.It \e(^o
-.Pq circumflex o
-.It \e(^u
-.Pq circumflex u
-.It \e(,C
-.Pq cedilla C
-.It \e(,c
-.Pq cedilla c
-.It \e(/L
-.Pq stroke L
-.It \e(/l
-.Pq stroke l
-.It \e(/O
-.Pq stroke O
-.It \e(/o
-.Pq stroke o
-.It \e(oA
-.Pq ring A
-.It \e(oa
-.Pq ring a
+Accents:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(a"    Ta \(a"        Ta Hungarian umlaut
+.It \e(a-    Ta \(a-        Ta macron
+.It \e(a.    Ta \(a.        Ta dotted
+.It \e(a^    Ta \(a^        Ta circumflex
+.It \e(aa    Ta \(aa        Ta acute
+.It \e\(aq   Ta \'          Ta acute
+.It \e(ga    Ta \(ga        Ta grave
+.It \e\(ga   Ta \`          Ta grave
+.It \e(ab    Ta \(ab        Ta breve
+.It \e(ac    Ta \(ac        Ta cedilla
+.It \e(ad    Ta \(ad        Ta dieresis
+.It \e(ah    Ta \(ah        Ta caron
+.It \e(ao    Ta \(ao        Ta ring
+.It \e(a\(ti Ta \(a~        Ta tilde
+.It \e(ho    Ta \(ho        Ta ogonek
+.It \e(ha    Ta \(ha        Ta hat (ASCII character)
+.It \e(ti    Ta \(ti        Ta tilde (ASCII character)
 .El
-.\" PARAGRAPH
 .Pp
-Monetary:
-.Bl -tag -width Ds -offset indent -compact
-.It \e(Cs
-.Pq Scandinavian
-.It \e(Do
-.Pq dollar
-.It \e(Po
-.Pq pound
-.It \e(Ye
-.Pq yen
-.It \e(Fn
-.Pq florin
-.It \e(ct
-.Pq cent
-.It \e(Eu
-.Pq Euro character glyph
-.It \e(eu
-.Pq Euro symbol
+Accented letters:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(\(aqA Ta \('A        Ta acute A
+.It \e(\(aqE Ta \('E        Ta acute E
+.It \e(\(aqI Ta \('I        Ta acute I
+.It \e(\(aqO Ta \('O        Ta acute O
+.It \e(\(aqU Ta \('U        Ta acute U
+.It \e(\(aqY Ta \('Y        Ta acute Y
+.It \e(\(aqa Ta \('a        Ta acute a
+.It \e(\(aqe Ta \('e        Ta acute e
+.It \e(\(aqi Ta \('i        Ta acute i
+.It \e(\(aqo Ta \('o        Ta acute o
+.It \e(\(aqu Ta \('u        Ta acute u
+.It \e(\(aqy Ta \('y        Ta acute y
+.It \e(\(gaA Ta \(`A        Ta grave A
+.It \e(\(gaE Ta \(`E        Ta grave E
+.It \e(\(gaI Ta \(`I        Ta grave I
+.It \e(\(gaO Ta \(`O        Ta grave O
+.It \e(\(gaU Ta \(`U        Ta grave U
+.It \e(\(gaa Ta \(`a        Ta grave a
+.It \e(\(gae Ta \(`e        Ta grave e
+.It \e(\(gai Ta \(`i        Ta grave i
+.It \e(\(gao Ta \(`i        Ta grave o
+.It \e(\(gau Ta \(`u        Ta grave u
+.It \e(\(tiA Ta \(~A        Ta tilde A
+.It \e(\(tiN Ta \(~N        Ta tilde N
+.It \e(\(tiO Ta \(~O        Ta tilde O
+.It \e(\(tia Ta \(~a        Ta tilde a
+.It \e(\(tin Ta \(~n        Ta tilde n
+.It \e(\(tio Ta \(~o        Ta tilde o
+.It \e(:A    Ta \(:A        Ta dieresis A
+.It \e(:E    Ta \(:E        Ta dieresis E
+.It \e(:I    Ta \(:I        Ta dieresis I
+.It \e(:O    Ta \(:O        Ta dieresis O
+.It \e(:U    Ta \(:U        Ta dieresis U
+.It \e(:a    Ta \(:a        Ta dieresis a
+.It \e(:e    Ta \(:e        Ta dieresis e
+.It \e(:i    Ta \(:i        Ta dieresis i
+.It \e(:o    Ta \(:o        Ta dieresis o
+.It \e(:u    Ta \(:u        Ta dieresis u
+.It \e(:y    Ta \(:y        Ta dieresis y
+.It \e(^A    Ta \(^A        Ta circumflex A
+.It \e(^E    Ta \(^E        Ta circumflex E
+.It \e(^I    Ta \(^I        Ta circumflex I
+.It \e(^O    Ta \(^O        Ta circumflex O
+.It \e(^U    Ta \(^U        Ta circumflex U
+.It \e(^a    Ta \(^a        Ta circumflex a
+.It \e(^e    Ta \(^e        Ta circumflex e
+.It \e(^i    Ta \(^i        Ta circumflex i
+.It \e(^o    Ta \(^o        Ta circumflex o
+.It \e(^u    Ta \(^u        Ta circumflex u
+.It \e(,C    Ta \(,C        Ta cedilla C
+.It \e(,c    Ta \(,c        Ta cedilla c
+.It \e(/L    Ta \(/L        Ta stroke L
+.It \e(/l    Ta \(/l        Ta stroke l
+.It \e(/O    Ta \(/O        Ta stroke O
+.It \e(/o    Ta \(/o        Ta stroke o
+.It \e(oA    Ta \(oA        Ta ring A
+.It \e(oa    Ta \(oa        Ta ring a
 .El
-.\" PARAGRAPH
 .Pp
-Greek letters:
-.Bl -tag -width Ds -offset indent -compact
-.It \e(*A
-.Pq Alpha
-.It \e(*B
-.Pq Beta
-.It \e(*C
-.Pq Xi
-.It \e(*D
-.Pq Delta
-.It \e(*E
-.Pq Epsilon
-.It \e(*F
-.Pq Phi
-.It \e(*G
-.Pq Gamma
-.It \e(*H
-.Pq Theta
-.It \e(*I
-.Pq Iota
-.It \e(*K
-.Pq Kappa
-.It \e(*L
-.Pq Lambda
-.It \e(*M
-.Pq Mu
-.It \e(*N
-.Pq Nu
-.It \e(*O
-.Pq Omicron
-.It \e(*P
-.Pq Pi
-.It \e(*Q
-.Pq Psi
-.It \e(*R
-.Pq Rho
-.It \e(*S
-.Pq Sigma
-.It \e(*T
-.Pq Tau
-.It \e(*U
-.Pq Upsilon
-.It \e(*W
-.Pq Omega
-.It \e(*X
-.Pq Chi
-.It \e(*Y
-.Pq Eta
-.It \e(*Z
-.Pq Zeta
-.It \e(*a
-.Pq alpha
-.It \e(*b
-.Pq beta
-.It \e(*c
-.Pq xi
-.It \e(*d
-.Pq delta
-.It \e(*e
-.Pq epsilon
-.It \e(*f
-.Pq phi
-.It \e(+f
-.Pq phi variant
-.It \e(*g
-.Pq gamma
-.It \e(*h
-.Pq theta
-.It \e(+h
-.Pq theta variant
-.It \e(*i
-.Pq iota
-.It \e(*k
-.Pq kappa
-.It \e(*l
-.Pq lambda
-.It \e(*m
-.Pq mu
-.It \e(*n
-.Pq nu
-.It \e(*o
-.Pq omicron
-.It \e(*p
-.Pq pi
-.It \e(+p
-.Pq pi variant
-.It \e(*q
-.Pq psi
-.It \e(*r
-.Pq rho
-.It \e(*s
-.Pq sigma
-.It \e(*t
-.Pq tau
-.It \e(*u
-.Pq upsilon
-.It \e(*w
-.Pq omega
-.It \e(*x
-.Pq chi
-.It \e(*y
-.Pq eta
-.It \e(*z
-.Pq zeta
-.It \e(ts
-.Pq sigma terminal
+Special letters:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(-D    Ta \(-D        Ta Eth
+.It \e(Sd    Ta \(Sd        Ta eth
+.It \e(TP    Ta \(TP        Ta Thorn
+.It \e(Tp    Ta \(Tp        Ta thorn
+.It \e(.i    Ta \(.i        Ta dotless i
+.It \e(.j    Ta \(.j        Ta dotless j
 .El
-.\" PARAGRAPH
 .Pp
-Special symbols:
-.Bl -tag -width Ds -offset indent -compact
-.It \e0
-.Pq white-space
-.It \e(de
-.Pq degree
-.It \e(ps
-.Pq paragraph
-.It \e(sc
-.Pq section
-.It \e(dg
-.Pq dagger
-.It \e(dd
-.Pq double dagger
-.It \e(ci
-.Pq circle
-.It \e(ba
-.Pq bar
-.It \e(bb
-.Pq broken bar
-.It \e(co
-.Pq copyright
-.It \e(rg
-.Pq registered
-.It \e(tm
-.Pq trademarked
-.It \ee
-.Pq escape
-.El 
-.\" SECTION
-.Sh PREDEFINED STRINGS
-These are not recommended for use, as they differ across
-implementations:
+Currency:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(Do    Ta \(Do        Ta dollar
+.It \e(ct    Ta \(ct        Ta cent
+.It \e(Eu    Ta \(Eu        Ta Euro symbol
+.It \e(eu    Ta \(eu        Ta Euro symbol
+.It \e(Ye    Ta \(Ye        Ta yen
+.It \e(Po    Ta \(Po        Ta pound
+.It \e(Cs    Ta \(Cs        Ta Scandinavian
+.It \e(Fn    Ta \(Fn        Ta florin
+.El
 .Pp
-Mathematical:
-.Bl -tag -width Ds -offset indent -compact
-.It \e*(Ne
-.Pq not equal
-.It \e*(Ge
-.Pq greater-than-equal
-.It \e*(Le
-.Pq less-than-equal
-.It \e*(Gt
-.Pq greater-than
-.It \e*(Lt
-.Pq greater-than
-.It \e*(Pm
-.Pq plus-minus
-.It \e*(If
-.Pq infinity
-.It \e*(Pi
-.Pq pi
-.It \e*(Na
-.Pq NaN
+Units:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(de    Ta \(de        Ta degree
+.It \e(%0    Ta \(%0        Ta per-thousand
+.It \e(fm    Ta \(fm        Ta minute
+.It \e(sd    Ta \(sd        Ta second
+.It \e(mc    Ta \(mc        Ta micro
+.It \e(Of    Ta \(Of        Ta Spanish female ordinal
+.It \e(Om    Ta \(Om        Ta Spanish masculine ordinal
 .El
-.\" PARAGRAPH
 .Pp
-Special symbols:
-.Bl -tag -width Ds -offset indent -compact
-.It \e*(Ba
-.Pq vertical bar
-.It \e*(Am
-.Pq ampersand
-.It \e*R
-.Pq restricted mark
-.It \e*(Tm
-.Pq trade mark
+Greek letters:
+.Bl -column "Input" "Rendered" "Description" -offset indent -compact
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e(*A    Ta \(*A        Ta Alpha
+.It \e(*B    Ta \(*B        Ta Beta
+.It \e(*G    Ta \(*G        Ta Gamma
+.It \e(*D    Ta \(*D        Ta Delta
+.It \e(*E    Ta \(*E        Ta Epsilon
+.It \e(*Z    Ta \(*Z        Ta Zeta
+.It \e(*Y    Ta \(*Y        Ta Eta
+.It \e(*H    Ta \(*H        Ta Theta
+.It \e(*I    Ta \(*I        Ta Iota
+.It \e(*K    Ta \(*K        Ta Kappa
+.It \e(*L    Ta \(*L        Ta Lambda
+.It \e(*M    Ta \(*M        Ta Mu
+.It \e(*N    Ta \(*N        Ta Nu
+.It \e(*C    Ta \(*C        Ta Xi
+.It \e(*O    Ta \(*O        Ta Omicron
+.It \e(*P    Ta \(*P        Ta Pi
+.It \e(*R    Ta \(*R        Ta Rho
+.It \e(*S    Ta \(*S        Ta Sigma
+.It \e(*T    Ta \(*T        Ta Tau
+.It \e(*U    Ta \(*U        Ta Upsilon
+.It \e(*F    Ta \(*F        Ta Phi
+.It \e(*X    Ta \(*X        Ta Chi
+.It \e(*Q    Ta \(*Q        Ta Psi
+.It \e(*W    Ta \(*W        Ta Omega
+.It \e(*a    Ta \(*a        Ta alpha
+.It \e(*b    Ta \(*b        Ta beta
+.It \e(*g    Ta \(*g        Ta gamma
+.It \e(*d    Ta \(*d        Ta delta
+.It \e(*e    Ta \(*e        Ta epsilon
+.It \e(*z    Ta \(*z        Ta zeta
+.It \e(*y    Ta \(*y        Ta eta
+.It \e(*h    Ta \(*h        Ta theta
+.It \e(*i    Ta \(*i        Ta iota
+.It \e(*k    Ta \(*k        Ta kappa
+.It \e(*l    Ta \(*l        Ta lambda
+.It \e(*m    Ta \(*m        Ta mu
+.It \e(*n    Ta \(*n        Ta nu
+.It \e(*c    Ta \(*c        Ta xi
+.It \e(*o    Ta \(*o        Ta omicron
+.It \e(*p    Ta \(*p        Ta pi
+.It \e(*r    Ta \(*r        Ta rho
+.It \e(*s    Ta \(*s        Ta sigma
+.It \e(*t    Ta \(*t        Ta tau
+.It \e(*u    Ta \(*u        Ta upsilon
+.It \e(*f    Ta \(*f        Ta phi
+.It \e(*x    Ta \(*x        Ta chi
+.It \e(*q    Ta \(*q        Ta psi
+.It \e(*w    Ta \(*w        Ta omega
+.It \e(+h    Ta \(+h        Ta theta variant
+.It \e(+f    Ta \(+f        Ta phi variant
+.It \e(+p    Ta \(+p        Ta pi variant
+.It \e(+e    Ta \(+e        Ta epsilon variant
+.It \e(ts    Ta \(ts        Ta sigma terminal
 .El
-.\" PARAGRAPH
+.Sh PREDEFINED STRINGS
+Predefined strings are inherited from the macro packages of historical
+troff implementations.
+They are
+.Em not recommended
+for use, as they differ across implementations.
+Manuals using these predefined strings are almost certainly not
+portable.
 .Pp
-Enclosures:
-.Bl -tag -width Ds -offset indent -compact
-.It \e*q
-.Pq double-quote
-.It \e*(Rq
-.Pq right-double-quote
-.It \e*(Lq
-.Pq left-double-quote
-.It \e*(lp
-.Pq right-parenthesis
-.It \e*(rp
-.Pq left-parenthesis
+Their syntax is similar to special characters, using
+.Sq \e*X
+.Pq for a one-character escape ,
+.Sq \e*(XX
+.Pq two-character ,
+and
+.Sq \e*[N]
+.Pq N-character .
+.Bl -column "Input" "Rendered" "Description" -offset indent
+.It Em Input Ta Em Rendered Ta Em Description
+.It \e*(Ba   Ta \*(Ba       Ta vertical bar
+.It \e*(Ne   Ta \*(Ne       Ta not equal
+.It \e*(Ge   Ta \*(Ge       Ta greater-than-equal
+.It \e*(Le   Ta \*(Le       Ta less-than-equal
+.It \e*(Gt   Ta \*(Gt       Ta greater-than
+.It \e*(Lt   Ta \*(Lt       Ta less-than
+.It \e*(Pm   Ta \*(Pm       Ta plus-minus
+.It \e*(If   Ta \*(If       Ta infinity
+.It \e*(Pi   Ta \*(Pi       Ta pi
+.It \e*(Na   Ta \*(Na       Ta NaN
+.It \e*(Am   Ta \*(Am       Ta ampersand
+.It \e*R     Ta \*R         Ta restricted mark
+.It \e*(Tm   Ta \*(Tm       Ta trade mark
+.It \e*q     Ta \*q         Ta double-quote
+.It \e*(Rq   Ta \*(Rq       Ta right-double-quote
+.It \e*(Lq   Ta \*(Lq       Ta left-double-quote
+.It \e*(lp   Ta \*(lp       Ta right-parenthesis
+.It \e*(rp   Ta \*(rp       Ta left-parenthesis
+.It \e*(lq   Ta \*(lq       Ta left double-quote
+.It \e*(rq   Ta \*(rq       Ta right double-quote
+.It \e*(ua   Ta \*(ua       Ta up arrow
+.It \e*(va   Ta \*(va       Ta up-down arrow
+.It \e*(<=   Ta \*(<=       Ta less-than-equal
+.It \e*(>=   Ta \*(>=       Ta greater-than-equal
+.It \e*(aa   Ta \*(aa       Ta acute
+.It \e*(ga   Ta \*(ga       Ta grave
+.It \e*(Px   Ta \*(Px       Ta POSIX standard name
+.It \e*(Ai   Ta \*(Ai       Ta ANSI standard name
 .El
-.\" SECTION
+.Sh UNICODE CHARACTERS
+The escape sequences
+.Pp
+.Dl \e[uXXXX] and \eC\(aquXXXX\(aq
+.Pp
+are interpreted as Unicode codepoints.
+The codepoint must be in the range above U+0080 and less than U+10FFFF.
+For compatibility, the hexadecimal digits
+.Sq A
+to
+.Sq F
+must be given as uppercase characters,
+and points must be zero-padded to four characters; if
+greater than four characters, no zero padding is allowed.
+Unicode surrogates are not allowed.
+.Sh NUMBERED CHARACTERS
+For backward compatibility with existing manuals,
+.Xr mandoc 1
+also supports the
+.Pp
+.Dl \eN\(aq Ns Ar number Ns \(aq and \e[ Ns Cm char Ns Ar number ]
+.Pp
+escape sequences, inserting the character
+.Ar number
+from the current character set into the output.
+Of course, this is inherently non-portable and is already marked
+as deprecated in the Heirloom roff manual;
+on top of that, the second form is a GNU extension.
+For example, do not use \eN\(aq34\(aq or \e[char34], use \e(dq,
+or even the plain
+.Sq \(dq
+character where possible.
 .Sh COMPATIBILITY
-This section documents compatibility of
-.Nm
-with older or existing versions of
-.Xr groff 1 :
+This section documents compatibility between mandoc and other
+troff implementations, at this time limited to GNU troff
+.Pq Qq groff .
 .Pp
-.Bl -tag -width Ds -offset indent -compact
-.It \e(ss
-Renders differently in
-.Fl T Ns Ar ascii
-mode.
+.Bl -dash -compact
+.It
+The \eN\(aq\(aq escape sequence is limited to printable characters; in
+groff, it accepts arbitrary character numbers.
+.It
+In
+.Fl T Ns Cm ascii ,
+the
+\e(ss, \e(nm, \e(nb, \e(nc, \e(ib, \e(ip, \e(pp, \e[sum], \e[product],
+\e[coproduct], \e(gr, \e(-h, and \e(a. special characters render
+differently between mandoc and groff.
+.It
+In
+.Fl T Ns Cm html ,
+the \e(\(ti=, \e(nb, and \e(nc special characters render differently
+between mandoc and groff.
+.It
+The
+.Fl T Ns Cm ps
+and
+.Fl T Ns Cm pdf
+modes format like
+.Fl T Ns Cm ascii
+instead of rendering glyphs as in groff.
+.It
+The \e[radicalex], \e[sqrtex], and \e(ru special characters have been omitted
+from mandoc either because they are poorly documented or they have no
+known representation.
 .El
-.\" SECTION
 .Sh SEE ALSO
-.Xr mandoc 1
-.\" SECTION
+.Xr mandoc 1 ,
+.Xr man 7 ,
+.Xr mdoc 7 ,
+.Xr roff 7
 .Sh AUTHORS
 The
 .Nm
-utility was written by 
-.An Kristaps Dzonsons Aq kristaps@kth.se .
+manual page was written by
+.An Kristaps Dzonsons Aq Mt kristaps@bsd.lv .
+.Sh CAVEATS
+The predefined string
+.Sq \e*(Ba
+mimics the behaviour of the
+.Sq \&|
+character in
+.Xr mdoc 7 ;
+thus, if you wish to render a vertical bar with no side effects, use
+the
+.Sq \e(ba
+escape.