The
tilde (~) is a
grapheme with several uses.
The name of the character comes from
Spanish, from the
Latin ''titulus'' meaning a title or superscription, and is pronounced , in English, or , in Spanish. It was originally written over a letter as a mark of
abbreviation, but has since acquired a number of other uses as a
diacritic mark or a character in its own right. In the latter capacity (especially in
lexicography) it is also sometimes known as the
swung dash (usually lengthened to ),
twiddle or the
squiggle.
Diacritical use
In languages, the tilde is a
diacritical mark (
~) placed over a
letter to indicate a change in pronunciation, such as
nasalization.
It was first used in the
polytonic orthography of
Ancient Greek, as a variant of the
circumflex accent, representing a rise in
pitch followed by a return to standard pitch.
Later, it was used to make
abbreviations in medieval
Latin documents. When an "n" or "m" followed a vowel, it was often omitted, and a tilde (i.e. a small "n") was placed over the preceding vowel to indicate the missing letter. This is the origin of the use of tilde to indicate nasalization. The practice of using the tilde over a vowel to indicate omission of an "n" or "m" continued in printed books in
French as a means of reducing text length until the 17th century. It was also used in
Spanish. The tilde was also used occasionally to make other abbreviations, such as over the letter "q" to signify the word ''que'' (Fr. "that").
Languages where the tilde is part of the symbol "
ñ", for the
palatal nasal consonant include:
Basque
Galician
Guarani
Mapudungun
Spanish. The tilded "n" ("ñ") developed from the grapheme "nn". It is usually regarded as a separate letter called ''eñe'', rather than a letter-diacritic combination. The word ''tilde'' often designates any accent mark; for example, the acute accent in ''José'' is also called a ''tilde'' in Spanish.
Tetum
Languages and alphabets where the tilde is used as a sign of
nasalization include:
In the International Phonetic Alphabet (IPA). For example, is the transcription of the pronunciation of the word "Lyon" in French.
Portuguese. The tilde originated as a small "n" written above another letter, marking a Latin letter which had been elided. It indicates nasalization of the base vowel: "ã", "õ".
Several native languages of South America, such as Guarani and Nheengatu.
Languages and alphabets that use the tilde for other purposes:
Estonian. The symbol "õ" stands for the close-mid back unrounded vowel, and it is considered an independent letter.
Guarani. The tilded "G̃" (note that G/g with tilde is not available as a precomposed glyph in Unicode) stands for the velar nasal consonant.
In the International Phonetic Alphabet (IPA), the tilde is used ''through'' a symbol to mark velarization. For instance, is the Australian English pronunciation of "cool", with the "dark l".
Vietnamese. A tilde over a vowel represents a dipping tone (''ngã'').
Lexicography
In
dictionaries, both bilingual and monolingual, the tilde is often referred to as a
swung dash. It is often used to replace the
headword of an entry when it occurs within the entry, in order to save space. For example, ''~ enough'' would represent ''ironically enough'' at the entry for ''ironically''.
Logic
In written mathematical
logic, it represents
negation (e.g. "~''p''" equals "not ''p''".) Modern use has been replacing the tilde with the exclamation mark (!) for this purpose, to avoid confusion with
equivalence relations.
Punctuation
It is sometimes used as
punctuation (instead of a
hyphen or
dash) between two
numbers, to indicate that they are a
range, rather than
subtraction, or a hyphenated number (such as a part number or model number).
Japanese and other
East Asian languages almost always use this convention, but it is often done for clarity in other languages as well. For example: 12~15 means "12 to 15", ~3 means "up to three" and 100~ means "100 and greater." However in English, a tilde preceding a number sometimes represents an approximation (see the following section).
In Japanese, the tilde is also used to separate a title and a subtitle in the same line. A
colon is usually used in English for this purpose.
When used in conversations via email or instant messenger it might have been intended as a
sarcasm mark or, in Asian cultures, as an extension of the final syllable to produce the same effect as "whyyyyyy" with "why~~". Used at the end of a word or sentence in fanfiction, it often denotes something said in a sing-song voice, or similar to the use in instant messengers and email, depending on context.
Mathematics
In
mathematics, the tilde, sometimes pronounced "twiddle," is often used to denote an
equivalence relation between two objects. Thus "''x'' ~ ''y''" means "''x'' is equivalent to ''y''". (Note that this is usually quite different from stating that ''x''
equals ''y''.) The expression "''x'' ~ ''y''" is sometimes read aloud as "''x'' twiddles ''y''," perhaps as an analogue to the verbal expression of "''x'' = ''y''."
There are two common contexts in which "~" is used to denote particular equivalence relations: It can be used to denote the
asymptotical equality of two functions. For example, ''f''(''x'') ~ ''g''(''x''), means that lim
x→∞ ''f''(''x'')/''g''(''x'') = 1. Additionally, in
statistics and
probability theory, ~ means "is distributed as." See
random variable.
There is also a triple-tilde (
≋), which is often used to show
congruence, an equivalence relation in geometry.
In
English it is sometimes used to represent
approximation, for example ~10 would mean "approximately 10." Similar symbols are used in mathematics, such as in π ≈ 3.14, "
π is about equal to 3.14." Since the double-tilde (
≈) is not available from the
keyboard except on the
Macintosh (where it is Option-x on English
layouts), the tilde (~) became a substitute for use in
typed entry.
A tilde is also used to indicate "approximately equal to" (e.g. 1.902 ~= 2). This usage probably developed as a typed alternative to the
libra symbol used for the same purpose in written mathematics, which is an equal sign (=) with the upper bar replaced by a bar with an upward hump or loop in the middle or, sometimes, a tilde.
see Approximation . The symbol "≈" is also used for this purpose.
A tilde placed below a letter in mathematics can represent a vector quantity.
Computing
Directories and URLs
In
Unix shells, the tilde indicates the current user's
home directory (e.g.,
/home/''username''). When prepended to a particular username, it indicates that user's home directory (e.g.,
~janedoe for the home directory of user
janedoe, typically
/home/janedoe). When some Unix shell commands overwrite a file, they can be made to keep a backup by renaming the original file as
filename~.
Used in
URLs on the
World Wide Web, it often denotes a personal website on a
Unix-based server. For example,
http://www.example.com/~johndoe/ might be the personal web site of John Doe. This mimics the Unix shell usage of the tilde. However, when accessed from the web, file access is usually directed to a
subdirectory in the user's home directory, such as
/home/''username''/public_html or
/home/''username''/www.
In URLs, the characters %7E (or %7e) may substitute a tilde if an input device lacks a tilde key. Thus,
http://www.example.com/~johndoe/ and
http://www.example.com/%7Ejohndoe/ are essentially the same URL.
Computer languages
It is used in the
Perl programming language as part of the pattern match operators for
regular expressions:
$a =~ /''regex''/ returns true if the variable is matched.
$a !~ /''regex''/ returns false if the variable is matched.
The popularity of Perl's regular expression and syntax has led to the use of these operators in other programming languages, such as
Ruby or the
SQL variant of the database
PostgreSQL.
In the
C and
C++ programming languages, the tilde character is used as an
operator to invert all
bits of an
integer (bitwise NOT), following the notation in logic (an
! causes a logical NOT, instead). In C++, the tilde is also used as the first character in a
class's
method name (where the rest of the name must be the same name as the class) to indicate a
destructor - a special method which is called at the end of the
object's life.
In the
D programming language, the tilde is used as an
array concatenation operator, as well as to indicate an object destructor.
In the
CSS stylesheet language, the tilde is used for the indirect adjacent combinator as part of a selector.
In the
Inform programming language, the tilde is used to indicate a quotation mark inside a quoted string.
In
Max/MSP, a tilde is used to denote objects that process at the computer's sampling rate, i.e. mainly those that deal with sound.
In "text mode" of the
LaTeX typesetting language a stand-alone tilde can be obtained with
\~{} and for use as a diacritics, e.g., like
\~{n} rendering "ñ".
In "math mode" a stand-alone tilde can be written as
\tilde{~} and as diacritics, e.g.,
\tilde{x}. For a wider tilde the
\widetilde can be used. The
\sim command produce a tilde-like character that is often used in
probability mathematical
equations, and the double-tilde is obtained with
\approx.
In both text and math mode a tilde on its own (
~) is rendering a white space with no line breaking.
The Emacs text editor forms the names used for backup files by appending a tilde to the original file name.
Microsoft filenames
The tilde was part of
Microsoft's
filename mangling scheme when it developed the
VFAT filesystem. This upgrade introduced long filenames to
Microsoft Windows, and permitted additional characters (such as the space) to be part of filenames, which were prohibited in previous versions. Programs written prior to this development could only access filenames in the so-called 8.3 format—the filenames consisted of a maximum of eight alphanumeric characters, followed by a period, followed by three more alphanumeric characters. In order to permit these legacy programs to access files in the VFAT filesystem, each file had to be given two names—one long, more descriptive one, and one that conformed to the 8.3 format. This was accomplished with a name-mangling scheme in which the first six characters of the filename are followed by a tilde and a digit. For example, "
Program Files" becomes "
PROGRA~1".
Also, the tilde symbol is used to prefix hidden temporary files that are created when a document is opened in Windows. For example, when you open a Word document called "Document1.doc," a file called "~ocument1.doc" will be created in the same directory. This file contains information about which user has the file open, to prevent multiple users from attempting to change a document at the same time.
Other uses
Computer programmers use the tilde in various ways and often call the symbol (as opposed to the diacritic) a
squiggle or a
twiddle. According to the
Jargon File, other synonyms sometimes used in
programming include
not,
approx,
wiggle,
enyay (after ''
eñe'') and (humorously)
sqiggle.
In
Google search, the tilde entered before a search query word displays listings with that word and synonyms of it.
[www.google.com ]
In
MediaWiki, three subsequent tildes (
~~~) create a "signature" (which can be customised by the user), five subsequent tildes (
~~~~~) result the time in
UTC, and four subsequent tildes (
~~~~) result in signature followed by the time in UTC.
References
