<P> The tilde (/ ˈtɪldə /; _̃ or ~) is a grapheme with several uses . The name of the character came into English from Spanish and from Portuguese, which in turn came from the Latin titulus, meaning "title" or "superscription". </P> <P> The reason for the name was that it was originally written over a letter as a scribal abbreviation, as a "mark of suspension", shown as a straight line when used with capitals . Thus the commonly used words Anno Domini were frequently abbreviated to A Dñi, an elevated terminal with a suspension mark placed over the "n". Such a mark could denote the omission of one letter or several letters . This saved on the expense of the scribe's labour and the cost of vellum and ink . Medieval European charters written in Latin are largely made up of such abbreviated words with suspension marks and other abbreviations; only uncommon words were given in full . The tilde has since been applied to 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 additional similar characters for different roles . In lexicography, the latter kind of tilde and the swung dash (⁓) are used in dictionaries to indicate the omission of the entry word . </P> <P> This symbol (in English) informally means "approximately", "about", or "around", such as "~ 30 minutes before", meaning "approximately 30 minutes before". It can mean "similar to", including "of the same order of magnitude as", such as: "x ~ y" meaning that x and y are of the same order of magnitude . Another approximation symbol is the double - tilde ≈, meaning "approximately equal to", the critical difference being the subjective level of accuracy: ≈ indicates a value which can be considered functionally equivalent for a calculation within an acceptable degree of error, whereas ~ is usually used to indicate a larger, possibly significant, degree of error . The tilde is also used to indicate "equal to" or "approximately equal to" by placing it over the "=" symbol, like so: ≅ . </P> <Table> <Tr> <Td> </Td> <Td> This section does not cite any sources . Please help improve this section by adding citations to reliable sources . Unsourced material may be challenged and removed . (February 2016) (Learn how and when to remove this template message) </Td> </Tr> </Table>

What does a tilde over an equal sign mean
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