Originally Posted by
derpderp
The tilde ( or ~; pronounced /ˈtɪldə/) is a grapheme with several uses. The name of the character comes from Spanish and Portuguese, from the Latin titulus meaning "title" or "superscription", though the term tilde has evolved and now has a different meaning in linguistics.
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. These are encoded in Unicode at U+0303 ̃ combining tilde and U+007E ~ tilde (as a spacing character). And there are more similar characters for different roles. Especially in lexicography the tilde as a separate character or swung dash is used in dictionaries to indicate the omission of the entry word.
The "~" used in math is for saying something is 'equivalent to'