Tilde: Difference between revisions

Punctuation marks
apostrophe ’  ' brackets [ ]  ( )  { }  ⟨ ⟩ colon  : comma , dashes ‒  –  —  ― ellipses …  ...  . . .  ⋯ exclamation marks  ! ¡ full stop, period . hyphens ‐ - interpunct · interrobangs ‽ ⸘ question marks  ? ¿ quotation marks ‘ ’  “ ”  ' '  " " ‹ ›  « » semicolon  ; slash, stroke, solidus /
In other scripts
Chinese Hebrew Japanese Korean
Related
Diacritics Whitespace characters Word dividers Typographic symbols
Category
v t e

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 til-de. 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), a tilde is sometimes confused with a swung dash (usually lengthened to ～) which is used in dictionaries to indicate the omission of a word^[1].

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 and Portuguese. The tilde was also used occasionally to make other abbreviations, such as over the letter "q" to signify the word que ("that").

The tilded "n" ("ñ") developed from the digraph "nn" in Spanish. It is usually regarded as a separate letter called eñe (IPA ['eɲe]), rather than a letter-diacritic combination. In addition, the word tilde can refer to any diacritic in this language; for example, the acute accent in José is also called a tilde in Spanish. Current languages in which the tilded "n" ("ñ") is used for the palatal nasal consonant /ɲ/ include:

• Basque
• Galician
• Guarani
• Mapudungun
• Spanish
• Tetum

It is also as a small "n" that the tilde originated when written above another letters, marking a Latin "n" which had been elided in old Galician-Portuguese. It indicates nasalization of the base vowel: mão "hand", from Lat. manu-; razões "reasons", from Lat. rationes. Current languages and alphabets in which the tilde is used as a sign of nasalization include:

• Portuguese
• Several native languages of South America, such as Guarani and Nheengatu.
• In the International Phonetic Alphabet (IPA) and many other phonetic alphabets. For example, [ljɔ̃] is the transcription of the pronunciation of the word "Lyon" in French.

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, [kʊːɫ] is the Australian English pronunciation of "cool", with the "dark l".
• Vietnamese. A tilde over a vowel represents a dipping tone (ngã).

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".

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.

It can approximate the sine wave symbol (∿, U+223F), which is used in electronics to indicate alternating current, in place of +, −, or ⎓ for direct current.

In some languages (though not English), a tilde-like wavy dash may be used as punctuation (instead of an unspaced hyphen or en-dash) between two numbers, to indicate 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 some other languages as well. For example, 12~15 means "12 to 15", ~3 means "up to three" and 100~ means "100 and greater." In English, the tilde is often used to express ranges and model numbers in electronics but rarely in formal grammar or type-set documents, as a wavy dash 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 text communications, it often denotes something said in a sing-song voice, or similar to the use in instant messengers and email, depending on context.

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.

A tilde can also be used to represent Similarity. In modern Geometry, polygons can be similar to one another, and similarity can be expressed as (e.g. Triangle ABC ~ (is similar to) Triangle DEF.) This is often used to relate polygons that have a geometric similarity to others, such as when using ratios and proportions to compare polygons.

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. [Also see Approximation]. The symbol "≈" is also used for this purpose.

A tilde placed below a letter in mathematics can represent a vector quantity.

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.

The tilde is used in the Awk programming language as part of the pattern match operators for regular expressions:

• variable ~ /regex/ returns true if the variable is matched.
• variable !~ /regex/ returns false if the variable is matched.

A variant of this, with the plain tilde replaced with =~, was adopted in Perl, and this semi-standardization 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.