backslash

The backslash, officially called the reverse solidus, is a typographic character represented by the symbol "\". It is used in computing, mathematics, and typography, with its meaning varying by context. It contrasts with the forward slash "/".

In Unicode it is U+005C and in ASCII decimal 92. In most fonts it appears as a diagonal line slanting from the upper left to the lower right. Its appearance can vary by font and rendering.

In Windows and DOS, it is the directory separator in file paths (for example C:\Program Files). In programming languages, the backslash is commonly the escape character in string literals, introducing sequences such as \n for newline, \t for tab, and \\ for a literal backslash; also used to escape quotes. It starts control sequences in TeX/LaTeX (for example \section) and is used to denote command names in many scripting languages. In regular expressions, backslashes escape metacharacters and can introduce token classes such as \d or \w.

In mathematics, A \ B denotes set difference (elements in A that are not in B). The symbol also appears in various notational conventions in logic, linguistics, and programming.

The backslash arises from typographic conventions and computing needs in the 20th century and has no single universal meaning; practitioners rely on context to interpret it correctly.