Mathematicians frequently use an accent to create a new variable from an old one, usually to denote a mathematical object with some specific functional relationship with the old one. The most commonly used accents are bar, check, circumflex, and tilde.

**Example **

Let \(X\) be a subspace of a space \(S\), and let \(\bar{X}\) be the closure of \(X\) in \(S\).

**Remark**

Like accents, primes (the symbol ') may be used to denote objects functionally related to the given objects, but they are also used to create new names for objects of the same type. This latter appears to be an uncommon use for accents.