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DEFINITIONS OF TERMS USED IN THIS MANUAL
#TERMS_TYPESETTINGTypesetting Terms #TERMS_GROFFGroff Terms #TERMS_MOMMom Document Processing Terms I use a number of typesetting-specific and groff-specific terms
throughout this documentation, as well as a few terms that apply
to 
mom herself.  To make life easier, I'll explain
them here.  Refer back to this section should you encounter a word
or concept you're not familiar with.  Words in these definitions that
are defined elsewhere in this section are marked with asterisks.
	
Typesetting terms
	
#TERMS_ASCENDERAscender 	
#TERMS_BASELINEBaseline 	
#TERMS_BALLOTBOXBallot box 	
#TERMS_BULLETBullet 	
#TERMS_CAPHEIGHTCap-height 	
#TERMS_DESCENDERDescender 	
#TERMS_DISCRETIONARYHYPHENDiscretionary hyphen 	
#TERMS_DROPCAPDrop cap 	
#TERMS_EMEm/en 	
#TERMS_FAMILYFamily 	
#TERMS_FIGURESPACEFigure space/Digit space 	
#TERMS_FIXEDWIDTHSPACEFixed width space 	
#TERMS_FONTFont 	
#TERMS_FORCEForce justify 	
#TERMS_JUSTJustify/justification 	
#TERMS_GUTTERGutter 	
#TERMS_KERNKerning 	
#TERMS_KERNUNITKern Units 	
#TERMS_LEADINGLead/leading     
	
#TERMS_LEADERLeaders 	
#TERMS_LIGATURESLigature     
	
#TERMS_PICASPOINTSPicas/Points 	
#TERMS_PSPoint Size 	
#TERMS_QUADQuad 	
#TERMS_RAGRag 	
#TERMS_SOLIDSolid/set solid 	
#TERMS_TRACKKERNINGTrack kerning/Line kerning 	
#TERMS_UNBREAKABLESPACEUnbreakable space 	
#TERMS_WORDSPACEWord space 	
#TERMS_XHEIGHTx-height Ascender The portion of a letter that extends above the bowl.  For example,
the letters a, c, and e have no ascenders.  The letters b, d, and h
do.
Baseline The imaginary line on which the bottoms of capital letters and the
bowls of lower case letters rest.
Ballot box An unfilled square, usually *cap-height in size,
typically placed beside items in a checklist.
Bullet A small, filled circle typically found beside items or points in
a list.
Cap-height The height of the tallest capital letter in a given
*font at the current *point
size
.
Descender The portion of a letter that extends beneath the
*baseline (j, q, y are letters with descenders).
Discretionary hyphen A symbol inserted between two syllables of a word that indicates to a
typesetting program the legal hyphenation points in the word.  Normally,
if hyphenation is turned on, groff knows where to hyphenate words.
However, hyphenation being what it is (in English, at any rate),
groff doesn't always get it right.  Discretionary hyphens make sure
it does.  In the event that the word doesn't need to be hyphenated
at all, groff leaves them alone.  In groff, the discretionary hyphen is
entered with
	\%
(backslash followed by a percent).
Drop cap A large, usually upper-case letter that introduces the first
paragraph of a document or section thereof.  The top of the drop
cap usually lines up with the top of the first line of the
paragraph, and typically "drops" several lines lower.
Text adjacent to the drop cap is indented to the right of the
letter until the bottom of the drop cap is reached, at which
point text reverts to the left margin.
Em/en A relative measurement equal to the width of the letter M at a
given 
*point size in a given *font.
Since most Ms are designed square, an em is usually (but sometimes
erroneously) considered to be the same size as the current point size
(i.e. if the point size of the type is 12, one em equals 12 points).
An en is equal to the width of a letter N (historically 2/3 of an em,
although groff treats an en as 1/2 of an em).  Typically, ems and
ens are used to measure indents, or to define the length of dashes
(long hyphens).
Family The collective name by which a collection of
*fonts are known, e.g.  Helvetica, Times Roman,
Garamond.
Figure space/Digit space A *fixed width space that has the width of one digit.  Used for
aligning numerals in, say, columns or numbered lists.  In groff,
the figure space is entered with
	\0
(backslash followed by a zero).
Fixed width space Equal to *word space, but does not expand or
contract when text is 
*justified.  In groff, fixed
width space is entered with
	\<space>
where <space> means "hit the spacebar on your keyboard."
Font The specific style of type within a *family,
e.g. roman, italic.  Groff understands four fonts within any given
family: roman, italic, bold, and bold italic.
Force justify
Sometimes, in *justified text, a line needs to be
broken short of the right margin.  Force justifying means telling a
typesetting program (like groff) that you want the line broken early
AND that you want the line's word spacing stretched to force the line
flush with the right margin.
Gutter The vertical whitespace separating columns of type.
Justify/justification Lines of type are justified when they're flush at both the left and
right margins.  Justification is the act of making both margins flush.
Some people use the terms "left justified" and "right justified"
to mean type where only the left (or right) margins align.  I don't.
See 
*quad.
Kerning Moving pairs of letters closer together to remove excess
whitespace between them.  In the days before phototypesetting,
type was set from small, rectangular blocks of wood or metal, each
block having exactly one letter.  Because the edge of each block
determined the edge of each letter, certain letter combinations (TA,
for example) didn't fit together well and had to be morticed by hand
to bring them visually closer.  Modern typesetting systems usually
take care of kerning automatically, but they're far from perfect.
Professional typesetters still devote a lot of time to fitting letters
and punctuation together properly.
Kern Units A relative distance equal to 1/36 of the current
*point size.  Used between individual letters
for 
*kerning.  Different typesetting systems use
different values (1/54 is popular), and sometimes call kern units by
a different name.
Experts:
A kern unit has nothing to do with groff
machine units.
Lead/leading The distance from the *baseline of one line of
type to the line of type immediately beneath it.  Pronounced "ledding."
Also called line spacing.  Usually measured in 
*points.
In case you're interested... In previous centuries,
lines of type were separated by thin strips of -- you guessed it
-- lead.  Lines of type that had no lead between them were said to
be "set solid." Once you began separating them with strips
of lead, they were said to be "leaded", and the spacing was
expressed in terms of the number of 
*points of lead.
For this reason, "leading" and "line spacing"
aren't, historically speaking, synonymous.  If type was set 10 on 12,
for example, the leading was 2 points, not 12.  Nowadays, however,
the two terms are used interchangeably to mean the distance from
baseline to baseline.
Leaders Single characters used to fill lines, usually to their end.
So called because they "lead" the eye from one element
of the page to another.  For example, in the following (brief)
Table of Contents, the periods (dots) are leaders.
	Foreword............... 2
	Chapter 1.............. 5
	Chapter 2.............. 38
	Chapter 3.............. 60
Ligature Ligatures are letters joined together to form a single character.
The commonest are fi, fl, ff, ffi and ffl.  Others are ae and oe.
Occasionally, one sees an st ligature, but this is archaic and
quite rare.
Picas/Points There are twelve points in a pica, and six picas in an inch
(hence 72 points to the inch).  In the same way that gem-dealers
have always used their own system of measurement for weight (carats),
typographers have always used their own system of measurement for type.
Point Size The nominal size of type, measured in *points,
from the bottom of the longest 
*descender to the top
of the highest 
*ascender.  In reality, type is always
fractionally smaller than its point size.
Quad When only one margin of type is flush, lines of type are quadded in
the direction of the flush margin.  Therefore, quad left means the
left margin is flush, the right isn't.  Quad right means the right
margin is flush, the left isn't.  Quad center means neither the left
nor the right margin is flush; rather, lines of type are quadded on
both sides so that type appears centered on the page.
Rag Describes a margin that isn't flush.  Rag right means the right
margin isn't flush.  Rag left means the left margin isn't flush.
The expression "flush left/rag right" is sometimes used to describe
type that is 
*quadded left.
Solid/set solid When no *lead is added between lines of type
(i.e. the 
*point size and linespacing are the
same), the lines are said to be "set solid."
Track kerning/Line kerning Sometimes, it's advantageous to increase or decrease the amount of
space between every letter in a line by an equal (usually small)
amount, in order to fit more (or fewer) characters on the line.
The correct term is letter spacing, but track kerning and line kerning
(and sometimes, just "kerning") have come to mean the same thing.
Unbreakable space Equal to *word space, however words separated by
an unbreakable space will always be kept together on the same line.
Expands and contracts like word space.  Useful for proper names, which
should never be broken.  In groff, unbreakable space is entered with
	\~
(backslash followed by a tilde).
Word space The amount of whitespace between words.  When text is
*justified, word space expands or contracts to make
the margins flush.
x-height The height of a lower case letter x in a given font at a given
point size.  Generally used to mean the average height of the bowl
of lower case letters.
	
Groff terms
	
#TERMS_ALIASAlias 	
#TERMS_ARGUMENTSArguments 	
#TERMS_COMMENTLINESComment lines 	
#TERMS_CONTROLLINESControl Lines 	
#TERMS_FILLEDFilled lines 	
#TERMS_INLINESInline escapes 	
#TERMS_INPUTLINEInput line 	
#TERMS_MACROSMacros 	
#TERMS_UNITSMachine units 	
#TERMS_NUMERICARGUMENTNumeric argument 	
#TERMS_OUTPUTLINEOutput line 	
#TERMS_PRIMITIVESPrimitives 	
#TERMS_STRINGARGUMENTString Argument 	
#TERMS_UNITOFMEASUREUnit of measure 	
#TERMS_ZEROWIDTHCHARACTERZero-width character Alias A *macro invoked by a name different from its
"official" name.  For example, the official name of the
macro to change 
*family is FAMILY.
Its alias is 
FAM.  Aliases may be created for any
macro (via the
goodies.html#ALIASALIAS macro) provided the alias uses a name not already taken
by the 
mom macros or one of the groff
*primitives.  For a complete list of alias names
you must not use, see the
reserved.html#RESERVEDlist of reserved words .
Arguments Parameters or information needed by a *macroto do its job.  For example, in the macro
	.PT_SIZE 12
"12" is the argument.  In the macro
	.QUAD LEFT
LEFT is the argument.  Arguments are separated from macros by spaces.
Some macros require several arguments; each is separated by a space.
Comment Lines *Input lines introduced with the comment character
	\#
When processing output, groff silently ignores everything on the
line after the comment character.
Control Lines Instructions to groff that appear on a line by themselves,
which means that "control lines" are either
*macros or *groff primitives.
Control lines begin with a period or, occasionally, an apostrophe.
Filled lines/fill mode Automatic *justification or
*quadding.  In fill mode, the ends of lines as they
appear in your text editor are ignored.  Instead, words from adjoining
*input lines are added one at a time to the output
line until no more words fit.  Then, depending whether text is to
be 
*justified or *quadded (left,
right, or center), and depending on whether automatic hyphenation
is turned on, groff attempts to hyphenate the last word, or, barring
that, spreads and breaks the line (when justification is turned on) or
breaks and quads the line (when quadding is turned on).
Nofill mode (non-filled text) means that groff respects the ends
of lines as they appear in your text editor.
Inline escapes Instructions issued to groff that appear as part of an
*input line (as opposed to *macros,
which must appear on a line by themselves).  Inline escapes are always
introduced by the backslash character.  For example,
	A line of text with the word T\*[BU 2]oronto in it
contains the inline escape \*[BU 2] (which means "move the letter
'o' 2 
*kern units closer to the letter 'T'").
Mom's inline escapes always take the form
\*[ESCAPE], where ESCAPEis composed of capital letters, sometimes followed immediately
by a digit, sometimes followed by a space and a 
*numeric
argument
. Groff's escapes begin with the
backslash character but typically have no star and are in lower case.
For example, the 
mom escapes to move forward 6 points
on a line are either
	\*[FP6]  or  \*[FWD 6p]
while the 
groff escape for the same thing is
	\h'6p'
Input line A line of text as it appears in your text editor.
Macros Instructions embedded in a document that determine how groff processes
the text for output.  
mom's macros always begin with a
period, on a line by themselves, and must be typed in capital letters.
Typically, macros contain complex commands issued to groff -- behind
the scenes -- via groff 
*primitives.
Machine units A machine unit is 1/1000 of a *point when the
groff device is ps.  ("ps" means "PostScript"  --
the default device for which groff prepares output, and the device for
which 
mom was specifically designed.)
Numeric argument An *argument that has the form of a digit.
Numeric arguments can be built out of arithmetic expressions using
+, -, *, and / for plus, minus, times, and divided-by respectively.
If a numeric argument requires a 
*unit of measure,
a unit of measure must be appended to 
every digit in the
argument.  For example:
	.ALD 1i-1v
NOTE: groff does not respect the order of operations,
but rather evaluates arithmetic expressions from left to right.
Parentheses must be used to circumvent this peculiarity.  Not to
worry, though.  The likelihood of more than just the occasional plus
or minus sign when using 
mom's macros is slim.
Output line A line of text as it appears in output copy.
Primitives The two-letter, lower case instructions groff uses as its
native command language, and out of which macros are built.
String Argument Technically, any *argument that is not numeric.
In this documentation, string argument means an argument that requires
the user to input text.  For example, in the 
*macro	.TITLE "My Pulitzer Novel"
"My Pulitzer Novel" is a string argument.
Because string arguments must be enclosed by double-quotes, you can't
use double-quotes as part of the string argument.  If you need
double-quotes to be part of a string argument, use the 
*inline
escapes
  \(lq and \(rq(leftquote and rightquote respectively) in place of the double-quote
character (").
Unit of measure The single letter after a *numeric argumentthat tells 
mom what measurement scale the argument
should use.  Commonly valid units are:
i  = inches
p  = points
P  = picas
c  = centimeters
m  = ems
n  = ens
v  = the current leading (line space) Units of measure must come immediately after the numeric argument (i.e.
with no space between the argument and the unit of measure), like this:
	.ALD 2v
	.LL  39P
	.IL  1i
The above example advances 2 line spaces and sets the line length to
39 picas with a left indent of 1 inch.
IMPORTANT: Most mom macros
that set the size or measure of something MUST be given a unit of
measure.  
mom's macros do not have default units
of measure.  There are a couple of exceptions, the most notable of
which are 
PT_SIZE and LS.  Both use
*points as the default unit of measure, which means
you don't have to append "p" to their argument.
You can enter decimal values for any unit of measure.  Different units
may be combined by adding them together (e.g. 1.5i+2m, which gives a
measure of 1-1/2 inches plus 2 ems).
NOTE: a pica is composed of 12 points,
therefore 12.5 picas is 12 picas and 6 points, not 12 picas
and 5 points.  If you want 12 picas and 5 points, you have to
enter the measure as 12P+5p.
Zero-width character The *inline escape that allows you to print a
literal period, apostrophe and, if 
*output linesare 
*filled, a space that falls at the beginning of
an 
*input line.  It looks like this:
	\&
(backslash followed by an ampersand).
Normally, groff interprets a period (or an apostrophe) at the beginning
of an input line as meaning that what follows is a 
*control
line
.  In fill modes, groff treats a space at the beginning
of an input line as meaning "start a new line and put a space
at the beginning of it." If you want groff to interpret periods
and apostrophes at the beginning of input lines literally (ie. print
them), or spaces at the beginning of input lines as just garden
variety word spaces, you must start the line with the zero-width
character.
	
Mom's Document Processing Terms
	
#TERMS_BLOCKQUOTEBlockquote 	
#TERMS_CONTROLMACROControl macro 	
#TERMS_DOCHEADERDocheader 	
#TERMS_EPIGRAPHEpigraph 	
#TERMS_FOOTERFooter 	
#TERMS_HEADHead 	
#TERMS_HEADERHeader 	
#TERMS_LINEBREAKLinebreak 	
#TERMS_PARAHEADParagraph head 	
#TERMS_QUOTEQuote 	
#TERMS_RUNNINGRunning text 	
#TERMS_SUBHEADSubhead 	
#TERMS_TOGGLEToggle Blockquote Cited material other than *quotes.
Typically set at a smaller point size than paragraph text, indented
from the left and right margins.  Blockquotes are
*filled.
Control macro Macros used in
docprocessing.html#DOCPROCESSINGdocument processing to control/alter the appearance of document elements (e.g. heads,
quotes, footnotes, 
*headers, etc.).
Document header/docheader Document information (title, subtitle, author, etc) output
at the top of page one.
Epigraph A short, usually cited passage that appears at the
beginning of a chapter, story, or other document.
Footer/page footer Document information (frequently author and title) output in
the bottom margin of pages 
after page one.  Not to be
confused with footnotes, which are considered part of
*running text.
Head A title that introduces a major section of a document.
Header/page header Document information (frequently author and title) output in
the top margin of pages 
after page one.
NOTE: In terms of content and style, headers and
*footers are the same; they differ only in their
placement on the page.  In most places in this documentation,
references to the content or style of headers applies equally to
footers.
Linebreak/author linebreak A horizontal gap in *running text, frequently
set off by typographic symbols such as asterisks or daggers.  Used to
indicate a shift in the content of a document (e.g. a scene change in a
short story).
Paragraph head A title joined to the body of a paragraph; hierarchically one
level beneath 
*subheads.
Quote A quote, to mom, is a line-for-line setting
of quoted material (e.g. poetry, song lyrics, or a snippet of
programming code).  You don't have to use
typesetting.html#BRBR with quotes.
Running text In a document formatted with mom, running
text means text that forms the body of the document, including
elements such as heads and subheads.  
*Docheaders,
*headers, *footers
 and page numbers are NOT part of
running text.
Subhead A title used to introduce secondary sections of a document;
hierarchically one level beneath sections introduced by
*heads.
Toggle A macro or tag that, when invoked without an argument,
begins something or turns a feature on, and, when invoked with
ANY argument, ends something or turns a feature off.  See
intro.html#TOGGLE_EXAMPLEExample 3 of the section
intro.html#MACRO_ARGSHow to read macro arguments .
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