Tilde

Tilde is an accent (~) placed over the Spanish n when pronounced ny (as in señor ) or the Portuguese a or o when nasalized (as in São Paulo ). It is used at times, over a vowel in phonetic transcription, indicating a nasal sound. This curvy diacritic mark is used in  various other languages, as well as for limited contexts in math, but should not be confused with other punctuation marks, such as the grave accent (‘)  or circumflex (^).

Uses and purpose of the tilde (~) 

The tilde(~), or the curvy mark used above letters as in Ã, is a grapheme which has several different uses. These uses often vary depending upon the language of the text it is used in. The word “tilde” originally came from the Latin word titulus meaning “title” or “superscription,” and made its way to English from Spanish. 

The tilde (~) symbol was originally written over a letter as a writing abbreviation or “mark of suspension” which allowed shorthand of a particular term. This was done frequently by scribes throughout history in order to save on the cost of supplies. Used in punctuation, the tilde is called the swung dash.

Practical uses of the tilde

The tilde (~) has varied uses across languages and with numerous functions. 

• The tilde (~) is a diacritic mark, which can indicate a particular pronunciation for the letter it is attached to, or be used as a spacing character. 
• In lexicography (a subject within linguistics) the tilde is used in dictionaries to indicate omission of an entry word. Informally, the symbol can be used to mean “approximately.” For example: “~30 minutes before sautéing the onions, chop the potatoes coarsely.”
• A tilde (~) can also indicate the words “similar to” as used in a mathematical equation. For example: “x~y”, means “x is similar in value to y”.
• In some languages such as Spanish and Basque, the tilde (~) is used over a particular letter in a word to indicate a change in pronunciation. For example: “Este año es el primero de la década.” (This year is the first of the decade.) In this case the tilde (~) represents a nasal “nyuh” sound instead of the traditional “en” sound.
• Also of note, in the Spanish language, the “n” (“en”) letter is included in the alphabet along with the “ñ” (“en-yay”).

The use of tilde (~) in other languages and subjects

The tilde (~) was first used in Ancient Greek to represent a vocal pitch rise followed by a return to standard pitch in pronunciation of a word.

The tilde (~) can also be used a palatal n, as is in the following languages: Asturian, Basque, Chamorro, Filipino, Galician, Guaraní, Mapudungun, Papiamento, Quechua, Spanish, and Tetum (primarily South American native languages). In Vietnamese, the tilde is used over a vowel to represent a creaky, rising tone as in the word ‘ngã’, which means “fall” in English.

The tilde (~) is used in phonetics to show intention of pronunciation, and it placed above a letter, below a letter, or superimposed onto the middle of a letter. Here is a summary:

When placed above the letter, the tilde indicates nasalization. 

If superimposed on the letter, the tilde indicates velarization or pharyngealization.

When placed below a letter, the tilde indicates laryngealization.

In the Estonian language, the symbol õ is considered an independent letter.

Finally, the symbol is also used in Arabic script to denote a long /a/ sound. 

In some languages in addition to English, the swung dash or tilde (~)  is used as punctuation to indicate a range between two numbers, as in “42~ 46.” Japanese and other East Asian languages typically use the symbol to indicate approximation with numbers, while Chinese uses the tilde(~)  and the full-width em dash interchangeably for number approximation.  In English, the tilde (~) is generally only used for this purpose in electronics or mathematical writing.