# Identifiers

*Identifiers* (names for user variables, functions etc.) must begin with a letter, and this letter may be followed by any combination of letters or digits, provided that the name is not a *reserved word* (see Chapter [Magma Semantics](../MagmaSemantics/index-magma-semantics.md#chapsem) for a complete list of reserved words). In this definition the underscore `_` is treated as a letter; but note that a single underscore is a reserved word. Identifier names are case-sensitive; that is, they are distinguished from one another by lower and upper case. *Intrinsic* Magma functions usually have names beginning with capital letters (current exceptions include `pCore, pQuotient` and the like, where the `p` indicates a prime). Note that these identifiers are *not* reserved words; that is, one may use names of intrinsic functions for variables.