@c This is part of the Emacs manual.
@c Copyright (C) 1985, 1986, 1987, 1993 Free Software Foundation, Inc.
@c See file emacs.texi for copying conditions.
@node Glossary, Key Index, Intro, Top
@unnumbered Glossary

@table @asis
@item Abbrev
An abbrev is a text string which expands into a different text string
when present in the buffer.  For example, you might define a short
word as an abbrev for a long phrase that you want to insert
frequently.  @xref{Abbrevs}.

@item Aborting
Aborting means getting out of a recursive edit (q.v.@:).  The
commands @kbd{C-]} and @kbd{M-x top-level} are used for this.
@xref{Quitting}.

@item Alt
Alt is the name of a modifier bit which a keyboard input character may
have.  To make a character Alt, type it while holding down the
@key{ALT} key.  Such characters are given names that start with
@kbd{Alt-} (usually written @kbd{A-} for short).  @xref{User Input,
Alt}.

@item Auto Fill Mode
Auto Fill mode is a minor mode in which text that you insert is
automatically broken into lines of fixed width.  @xref{Filling}.

@item Auto Saving
Auto saving is the practice of saving the contents of an Emacs buffer in
a specially-named file, so that the information will not be lost if the
buffer is lost due to a system error or user error.  @xref{Auto Save}.

@item Backup File
A backup file records the contents that a file had before the current
editing session.  Emacs makes backup files automatically to help you
track down or cancel changes you later regret making.  @xref{Backup}.

@item Balance Parentheses
Emacs can balance parentheses manually or automatically.  Manual
balancing is done by the commands to move over balanced expressions
(@pxref{Lists}).  Automatic balancing is done by blinking the
parenthesis that matches one just inserted (@pxref{Matching,,Matching
Parens}).

@item Bind
To bind a key sequence means to give it a binding (q.v.@:).
@xref{Rebinding}.

@item Binding
A key sequence gets its meaning in Emacs by having a binding, which is a
command (q.v.@:), a Lisp function that is run when the user types that
sequence.  @xref{Commands,Binding}.  Customization often involves
rebinding a character to a different command function.  The bindings of
all key sequences are recorded in the keymaps (q.v.@:).  @xref{Keymaps}.

@item Blank Lines
Blank lines are lines that contain only whitespace.  Emacs has several
commands for operating on the blank lines in the buffer.

@item Buffer
The buffer is the basic editing unit; one buffer corresponds to one
piece of text being edited.  You can have several buffers, but at any
time you are editing only one, the `selected' buffer, though several
can be visible when you are using multiple windows.  @xref{Buffers}.

@item Buffer Selection History
Emacs keeps a buffer selection history which records how recently each
Emacs buffer has been selected.  This is used for choosing a buffer to
select.  @xref{Buffers}.

@item Button Down Event
A button down event is the kind of input event generated right away when
you press a mouse button.  @xref{Mouse Buttons}.

@item C-
@samp{C} in the name of a character is an abbreviation for Control.
@xref{User Input,C-}.

@item C-M-
@samp{C-M-} in the name of a character is an abbreviation for
Control-Meta.  @xref{User Input,C-M-}.

@item Case Conversion
Case conversion means changing text from upper case to lower case or
vice versa.  @xref{Case}, for the commands for case conversion.

@item Characters
Characters form the contents of an Emacs buffer; see @ref{Text
Characters}.  Also, key sequences (q.v.@:) are usually made up of
characters (though they may include other input events as well).
@xref{User Input}.

@item Click Event
A click event is the kind of input event generated when you press a
mouse button and let it go without moving the mouse.  @xref{Mouse Buttons}.

@item Command
A command is a Lisp function specially defined to be able to serve as a
key binding in Emacs.  When you type a key sequence (q.v.@:), its
binding (q.v.@:) is looked up in the relevant keymaps (q.v.@:) to find
the command to run.  @xref{Commands}.

@item Command Name
A command name is the name of a Lisp symbol which is a command
(@pxref{Commands}).  You can invoke any command by its name using
@kbd{M-x} (@pxref{M-x}).

@item Comments
A comment is text in a program which is intended only for humans reading
the program, and which is marked specially so that it will be ignored
when the program is loaded or compiled.  Emacs offers special commands
for creating, aligning and killing comments.  @xref{Comments}.

@item Compilation
Compilation is the process of creating an executable program from source
code.  Emacs has commands for compiling files of Emacs Lisp code
(@pxref{Byte Compilation,, Byte Compilation, elisp, the Emacs Lisp
Reference Manual}) and programs in C and other languages
(@pxref{Compilation}).

@item Complete Key
A complete key is a key sequence which fully specifies one action to be
performed by Emacs.  For example, @kbd{X} and @kbd{C-f} and @kbd{C-x m}
are complete keys.  Complete keys derive their meanings from being bound
(q.v.@:) to commands (q.v.@:).  Thus, @kbd{X} is conventionally bound to
a command to insert @samp{X} in the buffer; @kbd{C-x m} is
conventionally bound to a command to begin composing a mail message.
@xref{Keys}.

@item Completion
Completion is what Emacs does when it automatically fills out an
abbreviation for a name into the entire name.  Completion is done for
minibuffer (q.v.@:) arguments when the set of possible valid inputs
is known; for example, on command names, buffer names, and
file names.  Completion occurs when @key{TAB}, @key{SPC} or @key{RET}
is typed.  @xref{Completion}.@refill

@item Continuation Line
When a line of text is longer than the width of the window, it
takes up more than one screen line when displayed.  We say that the
text line is continued, and all screen lines used for it after the
first are called continuation lines.  @xref{Basic,Continuation,Basic
Editing}.

@item Control Character
ASCII characters with octal codes 0 through 037, and also code 0177, do
not have graphic images assigned to them.  These are the Control
characters.  To type a Control character, hold down the @key{CTRL} key
and type the corresponding non-Control character.  @key{RET}, @key{TAB},
@key{ESC}, @key{LFD} and @key{DEL} are all control characters.
@xref{User Input}.

When you are using the X Window System, every non-control character has a
corresponding control character variant.

@item Copyleft
A copyleft is a notice giving the public legal permission to
redistribute a program or other work of art.  Copylefts are used by
left-wing programmers to give people equal rights, just as copyrights
are used by right-wing programmers to gain power over other people.

@item Current Buffer
The current buffer in Emacs is the Emacs buffer on which most editing
commands operate.  You can select any Emacs buffer as the current one.
@xref{Buffers}.

@item Current Line
The line point is on (@pxref{Point}).

@item Current Paragraph
The paragraph that point is in.  If point is between paragraphs, the
current paragraph is the one that follows point.  @xref{Paragraphs}.

@item Current Defun
The defun (q.v.@:) that point is in.  If point is between defuns, the
current defun is the one that follows point.  @xref{Defuns}.

@item Cursor
The cursor is the rectangle on the screen which indicates the position
called point (q.v.@:) at which insertion and deletion takes place.
The cursor is on or under the character that follows point.  Often
people speak of `the cursor' when, strictly speaking, they mean
`point'.  @xref{Basic,Cursor,Basic Editing}.

@item Customization
Customization is making minor changes in the way Emacs works.  It is
often done by setting variables (@pxref{Variables}) or by rebinding
key sequences (@pxref{Keymaps}).

@item Default Argument
The default for an argument is the value that will be assumed if you
do not specify one.  When the minibuffer is used to read an argument,
the default argument is used if you just type @key{RET}.
@xref{Minibuffer}.

@item Default Directory
When you specify a file name that does not start with @samp{/} or @samp{~},
it is interpreted relative to the current buffer's default directory.
@xref{Minibuffer File,Default Directory}.

@item Defun
A defun is a list at the top level of parenthesis or bracket structure
in a program.  It is so named because most such lists in Lisp programs
are calls to the Lisp function @code{defun}.  @xref{Defuns}.

@item @key{DEL}
@key{DEL} is a character that runs the command to delete one character of
text.  @xref{Basic,DEL,Basic Editing}.

@item Deletion
Deletion means erasing text without copying it into the kill ring
(q.v.@:).  The alternative is killing (q.v.@:).  @xref{Killing,Deletion}.

@item Deletion of Files
Deleting a file means erasing it from the file system.
@xref{Misc File Ops}.

@item Deletion of Messages
Deleting a message means flagging it to be eliminated from your mail
file.  Until you expunge (q.v.@:) the mail file, you can still undelete
the messages you have deleted.  @xref{Rmail Deletion}.

@item Deletion of Windows
Deleting a window means eliminating it from the screen.  Other windows
expand to use up the space.  The deleted window can never come back,
but no actual text is thereby lost.  @xref{Windows}.

@item Directory
File directories are named collections in the file system, within which
you can place individual files or subdirectories.
@xref{ListDir,,Directories}.

@item Dired
Dired is the Emacs facility that displays the contents of a file
directory and allows you to ``edit the directory'', performing
operations on the files in the directory.  @xref{Dired}.

@item Disabled Command
A disabled command is one that you may not run without special
confirmation.  The usual reason for disabling a command is that it is
confusing for beginning users.  @xref{Disabling}.

@item Down Event
Short for `button down event'.

@item Drag Event
A drag event is the kind of input event generated when you press a mouse
button, move the mouse, and then release the button.  @xref{Mouse
Buttons}.

@item Dribble File
A file into which Emacs writes all the characters that the user types
on the keyboard.  Dribble files are used to make a record for
debugging Emacs bugs.  Emacs does not make a dribble file unless you
tell it to.  @xref{Bugs}.

@item Echo Area
The echo area is the bottom line of the screen, used for echoing the
arguments to commands, for asking questions, and printing brief
messages (including error messages).  @xref{Echo Area}.

@item Echoing
Echoing is acknowledging the receipt of commands by displaying them (in
the echo area).  Emacs never echoes single-character key sequences;
longer key sequences echo only if you pause while typing them.

@item Error
An error occurs when an Emacs command cannot execute in the current
circumstances.  When an error occurs, execution of the command stops
(unless the command has been programmed to do otherwise) and Emacs
reports the error by printing an error message (q.v.@:).  Type-ahead
is discarded.  Then Emacs is ready to read another editing command.

@item Error Messages
Error messages are single lines of output printed by Emacs when the
user asks for something impossible to do (such as, killing text
forward when point is at the end of the buffer).  They appear in the
echo area, accompanied by a beep.

@item @key{ESC}
@key{ESC} is a character used as a prefix for typing Meta characters on
keyboards lacking a @key{META} key.  Unlike the @key{META} key (which,
like the @key{SHIFT} key, is held down while another character is
typed), the @key{ESC} key is pressed once and applies to the next
character typed.

@item Expunging
Expunging a mail file or Dired buffer means really discarding the
messages or files you have previously flagged for deletion.

@item Fill Prefix
The fill prefix is a string that should be expected at the beginning
of each line when filling is done.  It is not regarded as part of the
text to be filled.  @xref{Filling}.

@item Filling
Filling text means moving text from line to line so that all the lines
are approximately the same length.  @xref{Filling}.

@item Frame
A frame is a rectangular cluster of Emacs windows.  When using X Windows,
you can create more than one Emacs frame, each having its own X window,
and then you can subdivide each frame into Emacs windows as you wish.
@xref{Frames}.

@item Function Key
A function key is a key on the keyboard that does not correspond to any
character.  @xref{Function Keys}.

@item Global
Global means `independent of the current environment; in effect
throughout Emacs'.  It is the opposite of local (q.v.@:).  Particular
examples of the use of `global' appear below.

@item Global Abbrev
A global definition of an abbrev (q.v.@:) is effective in all major
modes that do not have local (q.v.@:) definitions for the same abbrev.
@xref{Abbrevs}.

@item Global Keymap
The global keymap (q.v.@:) contains key bindings that are in effect
except when overridden by local key bindings in a major mode's local
keymap (q.v.@:).  @xref{Keymaps}.

@item Global Substitution
Global substitution means replacing each occurrence of one string by
another string through a large amount of text.  @xref{Replace}.

@item Global Variable
The global value of a variable (q.v.@:) takes effect in all buffers
that do not have their own local (q.v.@:) values for the variable.
@xref{Variables}.

@item Graphic Character
Graphic characters are those assigned pictorial images rather than
just names.  All the non-Meta (q.v.@:) characters except for the
Control (q.v.@:) characters are graphic characters.  These include
letters, digits, punctuation, and spaces; they do not include
@key{RET} or @key{ESC}.  In Emacs, typing a graphic character inserts
that character (in ordinary editing modes).  @xref{Basic,,Basic Editing}.

@item Hardcopy
Hardcopy means printed output.  Emacs has commands for making printed
listings of text in Emacs buffers.  @xref{Hardcopy}.

@item @key{HELP}
You can type @key{HELP} at any time to ask what options you have, or to ask
what any command does.  The character @key{HELP} is really @kbd{C-h}.
@xref{Help}.

@item Hyper
Hyper is the name of a modifier bit which a keyboard input character may
have.  To make a character Hyper, type it while holding down the
@key{HYPER} key.  Such characters are given names that start with
@kbd{Hyper-} (usually written @kbd{H-} for short).  @xref{User Input,
Hyper}.

@item Inbox
An inbox is a file in which mail is delivered by the operating system.
Rmail transfers mail from inboxes to mail files (q.v.@:) in which the
mail is then stored permanently or until explicitly deleted.
@xref{Rmail Inbox}.

@item Indentation
Indentation means blank space at the beginning of a line.  Most
programming languages have conventions for using indentation to
illuminate the structure of the program, and Emacs has special
commands to adjust indentation.
@xref{Indentation}.

@item Insertion
Insertion means copying text into the buffer, either from the keyboard
or from some other place in Emacs.

@item Justification
Justification means adding extra spaces to lines of text to make them
come exactly to a specified width.  @xref{Filling,Justification}.

@item Keyboard Macros
Keyboard macros are a way of defining new Emacs commands from
sequences of existing ones, with no need to write a Lisp program.
@xref{Keyboard Macros}.

@item Key Sequence
A key sequence (key, for short) is a sequence of characters that, when
input to Emacs, is meaningful as a single unit.  If the key sequence is
enough to specify one action, it is a complete key (q.v.@:); if it is not
enough, it is a prefix key (q.v.@:).  @xref{Keys}.

@item Keymap
The keymap is the data structure that records the bindings (q.v.@:) of
key sequences to the commands that they run.  For example, the global
keymap binds the character @kbd{C-n} to the command function
@code{next-line}.  @xref{Keymaps}.

@item Keyboard Translation Table
The keyboard translation table is an array that translates the character
codes that come from the terminal into the character codes that make up
key sequences.  @xref{Keyboard Translations}.

@item Kill Ring
The kill ring is where all text you have killed recently is saved.
You can reinsert any of the killed text still in the ring; this is
called yanking (q.v.@:).  @xref{Yanking}.

@item Killing
Killing means erasing text and saving it on the kill ring so it can be
yanked (q.v.@:) later.  Some other systems call this ``cutting''.
Most Emacs commands to erase text do killing, as opposed to deletion
(q.v.@:).  @xref{Killing}.

@item Killing Jobs
Killing a job (such as, an invocation of Emacs) means making it cease
to exist.  Any data within it, if not saved in a file, is lost.
@xref{Exiting}.

@item List
A list is, approximately, a text string beginning with an open
parenthesis and ending with the matching close parenthesis.  In C mode
and other non-Lisp modes, groupings surrounded by other kinds of matched
delimiters appropriate to the language, such as braces, are also
considered lists.  Emacs has special commands for many operations on
lists.  @xref{Lists}.

@item Local
Local means `in effect only in a particular context'; the relevant
kind of context is a particular function execution, a particular
buffer, or a particular major mode.  It is the opposite of `global'
(q.v.@:).  Specific uses of `local' in Emacs terminology appear below.

@item Local Abbrev
A local abbrev definition is effective only if a particular major mode
is selected.  In that major mode, it overrides any global definition
for the same abbrev.  @xref{Abbrevs}.

@item Local Keymap
A local keymap is used in a particular major mode; the key bindings
(q.v.@:) in the current local keymap override global bindings of the
same key sequences.  @xref{Keymaps}.

@item Local Variable
A local value of a variable (q.v.@:) applies to only one buffer.
@xref{Locals}.

@item M-
@kbd{M-} in the name of a character is an abbreviation for @key{META},
one of the modifier keys that can accompany any character.
@xref{User Input}.

@item M-C-
@samp{M-C-} in the name of a character is an abbreviation for
Control-Meta; it means the same thing as @samp{C-M-}.  If your
terminal lacks a real @key{META} key, you type a Control-Meta character by
typing @key{ESC} and then typing the corresponding Control character.
@xref{User Input,C-M-}.

@item M-x
@kbd{M-x} is the key sequence which is used to call an Emacs command by
name.  This is how you run commands that are not bound to key sequences.
@xref{M-x}.

@item Mail
Mail means messages sent from one user to another through the computer
system, to be read at the recipient's convenience.  Emacs has commands for
composing and sending mail, and for reading and editing the mail you have
received.  @xref{Sending Mail}.  @xref{Rmail}, for how to read mail.

@item Mail File
A mail file is a file which is edited using Rmail and in which Rmail
stores mail.  @xref{Rmail}.

@item Major Mode
The Emacs major modes are a mutually exclusive set of options, each of
which configures Emacs for editing a certain sort of text.  Ideally,
each programming language has its own major mode.  @xref{Major Modes}.

@item Mark
The mark points to a position in the text.  It specifies one end of the
region (q.v.@:), point being the other end.  Many commands operate on
all the text from point to the mark.  Each buffer has its own mark.
@xref{Mark}.

@item Mark Ring
The mark ring is used to hold several recent previous locations of the
mark, just in case you want to move back to them.  Each buffer has its
own mark ring.  @xref{Mark Ring}.

@item Message
See `mail'.

@item Meta
Meta is the name of a modifier bit which a command character may have.
It is present in a character if the character is typed with the
@key{META} key held down.  Such characters are given names that start
with @kbd{Meta-} (usually written @kbd{M-} for short).  For example,
@kbd{M-<} is typed by holding down @key{META} and at the same time
typing @kbd{<} (which itself is done, on most terminals, by holding
down @key{SHIFT} and typing @kbd{,}).  @xref{User Input,Meta}.

@item Meta Character
A Meta character is one whose character code includes the Meta bit.

@item Minibuffer
The minibuffer is the window that appears when necessary inside the
echo area (q.v.@:), used for reading arguments to commands.
@xref{Minibuffer}.

@item Minibuffer History
The minibuffer history records the text you have specified in the past
for minibuffer arguments, so you can conveniently use the same text
again.  @xref{Minibuffer History}.

@item Minor Mode
A minor mode is an optional feature of Emacs which can be switched on
or off independently of all other features.  Each minor mode has a
command to turn it on or off.  @xref{Minor Modes}.

@item Minor Mode Keymap
A keymap that belongs to a minor mode and is active when that mode is
enabled.  Minor mode keymaps take precedence over the buffer's local
keymap, just as the local keymap takes precedence over the global
keymap.  @xref{Keymaps}.

@item Mode Line
The mode line is the line at the bottom of each window (q.v.@:), giving
status information on the buffer displayed in that window.  @xref{Mode
Line}.

@item Modified Buffer
A buffer (q.v.@:) is modified if its text has been changed since the
last time the buffer was saved (or since when it was created, if it
has never been saved).  @xref{Saving}.

@item Moving Text
Moving text means erasing it from one place and inserting it in
another.  The usual way to move text by killing (q.v.@:) and then
yanking (q.v.@:).  @xref{Killing}.

@item Named Mark
A named mark is a register (q.v.@:) in its role of recording a
location in text so that you can move point to that location.
@xref{Registers}.

@item Narrowing
Narrowing means creating a restriction (q.v.@:) that limits editing in
the current buffer to only a part of the text in the buffer.  Text
outside that part is inaccessible to the user until the boundaries are
widened again, but it is still there, and saving the file saves it
all.  @xref{Narrowing}.

@item Newline
@key{LFD} characters in the buffer terminate lines of text and are
called newlines.  @xref{Text Characters,Newline}.

@item Numeric Argument
A numeric argument is a number, specified before a command, to change
the effect of the command.  Often the numeric argument serves as a
repeat count.  @xref{Arguments}.

@item Option
An option is a variable (q.v.@:) that exists so that you can customize
Emacs by giving it a new value.  @xref{Variables}.

@item Overwrite Mode
Overwrite mode is a minor mode.  When it is enabled, ordinary text
characters replace the existing text after point rather than pushing
it to the right.  @xref{Minor Modes}.

@item Page
A page is a unit of text, delimited by formfeed characters (ASCII
control-L, code 014) coming at the beginning of a line.  Some Emacs
commands are provided for moving over and operating on pages.
@xref{Pages}.

@item Paragraphs
Paragraphs are the medium-size unit of English text.  There are
special Emacs commands for moving over and operating on paragraphs.
@xref{Paragraphs}.

@item Parsing
We say that certain Emacs commands parse words or expressions in the
text being edited.  Really, all they know how to do is find the other
end of a word or expression.  @xref{Syntax}.

@item Point
Point is the place in the buffer at which insertion and deletion
occur.  Point is considered to be between two characters, not at one
character.  The terminal's cursor (q.v.@:) indicates the location of
point.  @xref{Basic,Point}.
	
@item Prefix Argument
See `numeric argument'.

@item Prefix Key
A prefix key is a key sequence (q.v.@:) whose sole function is to
introduce a set of longer key sequences.  @kbd{C-x} is an example of
prefix key; any two-character sequence starting with @kbd{C-x} is
therefore a legitimate key sequence.  @xref{Keys}.

@item Primary Mail File
Your primary mail file is the file named @samp{RMAIL} in your home
directory, where all mail that you receive is stored by Rmail unless you
make arrangements to do otherwise.  @xref{Rmail}.

@item Prompt
A prompt is text printed to ask the user for input.  Printing a prompt
is called prompting.  Emacs prompts always appear in the echo area
(q.v.@:).  One kind of prompting happens when the minibuffer is used to
read an argument (@pxref{Minibuffer}); the echoing which happens when
you pause in the middle of typing a multicharacter key sequence is also
a kind of prompting (@pxref{Echo Area}).

@item Quitting
Quitting means cancelling a partially typed command or a running
command, using @kbd{C-g}.  @xref{Quitting}.

@item Quoting
Quoting means depriving a character of its usual special significance.
In Emacs this is usually done with @kbd{C-q}.  What constitutes special
significance depends on the context and on convention.  For example,
an ``ordinary'' character as an Emacs command inserts itself; so in
this context, a special character is any character that does not
normally insert itself (such as @key{DEL}, for example), and quoting
it makes it insert itself as if it were not special.  Not all contexts
allow quoting.  @xref{Basic,Quoting,Basic Editing}.

@item Read-Only Buffer
A read-only buffer is one whose text you are not allowed to change.
Normally Emacs makes buffers read-only when they contain text which
has a special significance to Emacs; for example, Dired buffers.
Visiting a file that is write protected also makes a read-only buffer.
@xref{Buffers}.

@item Recursive Editing Level
A recursive editing level is a state in which part of the execution of
a command involves asking the user to edit some text.  This text may
or may not be the same as the text to which the command was applied.
The mode line indicates recursive editing levels with square brackets
(@samp{[} and @samp{]}).  @xref{Recursive Edit}.

@item Redisplay
Redisplay is the process of correcting the image on the screen to
correspond to changes that have been made in the text being edited.
@xref{Screen,Redisplay}.

@item Regexp
See `regular expression'.

@item Region
The region is the text between point (q.v.@:) and the mark (q.v.@:).
Many commands operate on the text of the region.  @xref{Mark,Region}.

@item Registers
Registers are named slots in which text or buffer positions or
rectangles can be saved for later use.  @xref{Registers}.

@item Regular Expression
A regular expression is a pattern that can match various text strings;
for example, @samp{l[0-9]+} matches @samp{l} followed by one or more
digits.  @xref{Regexps}.

@item Repeat Count
See `numeric argument'.

@item Replacement
See `global substitution'.

@item Restriction
A buffer's restriction is the amount of text, at the beginning or the
end of the buffer, that is temporarily inaccessible.  Giving a buffer a
nonzero amount of restriction is called narrowing (q.v.@:).
@xref{Narrowing}.

@item @key{RET}
@key{RET} is a character than in Emacs runs the command to insert a
newline into the text.  It is also used to terminate most arguments
read in the minibuffer (q.v.@:).  @xref{User Input,Return}.

@item Saving
Saving a buffer means copying its text into the file that was visited
(q.v.@:) in that buffer.  This is the way text in files actually gets
changed by your Emacs editing.  @xref{Saving}.

@item Scrolling
Scrolling means shifting the text in the Emacs window so as to see a
different part of the buffer.  @xref{Display,Scrolling}.

@item Searching
Searching means moving point to the next occurrence of a specified
string.  @xref{Search}.

@item Selecting
Selecting a buffer means making it the current (q.v.@:) buffer.
@xref{Buffers,Selecting}.

@item Self-Documentation
Self-documentation is the feature of Emacs which can tell you what any
command does, or give you a list of all commands related to a topic
you specify.  You ask for self-documentation with the help character,
@kbd{C-h}.  @xref{Help}.

@item Sentences
Emacs has commands for moving by or killing by sentences.
@xref{Sentences}.

@item Sexp
A sexp (short for `s-expression') is the basic syntactic unit of Lisp
in its textual form: either a list, or Lisp atom.  Many Emacs commands
operate on sexps.  The term `sexp' is generalized to languages other
than Lisp, to mean a syntactically recognizable expression.
@xref{Lists,Sexps}.

@item Simultaneous Editing
Simultaneous editing means two users modifying the same file at once.
Simultaneous editing if not detected can cause one user to lose his
work.  Emacs detects all cases of simultaneous editing and warns the
user to investigate them.  @xref{Interlocking,,Simultaneous Editing}.

@item String
A string is a kind of Lisp data object which contains a sequence of
characters.  Many Emacs variables are intended to have strings as
values.  The Lisp syntax for a string consists of the characters in
the string with a @samp{"} before and another @samp{"} after.  A
@samp{"} that is part of the string must be written as @samp{\"} and a
@samp{\} that is part of the string must be written as @samp{\\}.  All
other characters, including newline, can be included just by writing
them inside the string; however, escape sequences as in C, such as
@samp{\n} for newline or @samp{\241} using an octal character code,
are allowed as well.

@item String Substitution
See `global substitution'.

@item Syntax Table
The syntax table tells Emacs which characters are part of a word,
which characters balance each other like parentheses, etc.
@xref{Syntax}.

@item Super
Super is the name of a modifier bit which a keyboard input character may
have.  To make a character Super, type it while holding down the
@key{SUPER} key.  Such characters are given names that start with
@kbd{Super-} (usually written @kbd{s-} for short).  @xref{User Input,
Super}.

@item Tag Table
A tag table is a file that serves as an index to the function
definitions in one or more other files.  @xref{Tags}.

@item Termscript File
A termscript file contains a record of all characters sent by Emacs to
the terminal.  It is used for tracking down bugs in Emacs redisplay.
Emacs does not make a termscript file unless you tell it to.
@xref{Bugs}.

@item Text
Two meanings (@pxref{Text}):

@itemize @bullet
@item
Data consisting of a sequence of characters, as opposed to binary
numbers, images, graphics commands, executable programs, and the like.
The contents of an Emacs buffer are always text in this sense.
@item
Data consisting of written human language, as opposed to programs,
or following the stylistic conventions of human language.
@end itemize

@item Top Level
Top level is the normal state of Emacs, in which you are editing the
text of the file you have visited.  You are at top level whenever you
are not in a recursive editing level (q.v.@:) or the minibuffer
(q.v.@:), and not in the middle of a command.  You can get back to top
level by aborting (q.v.@:) and quitting (q.v.@:).  @xref{Quitting}.

@item Transposition
Transposing two units of text means putting each one into the place
formerly occupied by the other.  There are Emacs commands to transpose
two adjacent characters, words, sexps (q.v.@:) or lines
(@pxref{Transpose}).

@item Truncation
Truncating text lines in the display means leaving out any text on a
line that does not fit within the right margin of the window
displaying it.  See also `continuation line'.
@xref{Basic,Truncation,Basic Editing}.

@item Undoing
Undoing means making your previous editing go in reverse, bringing
back the text that existed earlier in the editing session.
@xref{Undo}.

@item Variable
A variable is an object in Lisp that can store an arbitrary value.
Emacs uses some variables for internal purposes, and has others (known
as `options' (q.v.@:)) just so that you can set their values to
control the behavior of Emacs.  The variables used in Emacs that you
are likely to be interested in are listed in the Variables Index in
this manual.  @xref{Variables}, for information on variables.

@item Version Control
Version control systems keep track of multiple versions of a source file.
They provide a more powerful alternative to keeping backup files (q.v.@:).
@xref{Version Control}.

@item Visiting
Visiting a file means loading its contents into a buffer (q.v.@:)
where they can be edited.  @xref{Visiting}.

@item Whitespace
Whitespace is any run of consecutive formatting characters (space,
tab, newline, and backspace).

@item Widening
Widening is removing any restriction (q.v.@:) on the current buffer;
it is the opposite of narrowing (q.v.@:).  @xref{Narrowing}.

@item Window
Emacs divides a frame (q.v.@:) into one or more windows, each of which
can display the contents of one buffer (q.v.@:) at any time.
@xref{Screen}, for basic information on how Emacs uses the screen.
@xref{Windows}, for commands to control the use of windows.

@item Word Abbrev
Synonymous with `abbrev'.

@item Word Search
Word search is searching for a sequence of words, considering the
punctuation between them as insignificant.  @xref{Word Search}.

@item Yanking
Yanking means reinserting text previously killed.  It can be used to
undo a mistaken kill, or for copying or moving text.  Some other
systems call this ``pasting''.  @xref{Yanking}.
@end table

