The process of reading, i.e., of assembling the input into expressions, has a subprocess, called scanning, that assembles the characters into symbols. A symbol is a sequence of characters that form a lexical unit. The set of symbols consists of keywords, identifiers, strings, integers, and operator and delimiter symbols.
A keyword is a reserved word consisting entirely of lowercase letters (see Keywords). An identifier is a sequence of letters and digits that contains at least one letter and is not a keyword (see Identifiers). An integer is a sequence of digits (see Integers). A string is a sequence of arbitrary characters enclosed in double quotes (see Strings and Characters).
Operator and delimiter symbols are
+ - * / ^ ~ = <> < <= > >= := . .. -> , ; [ ] { } ( )
Note that during the process of scanning also all whitespace is removed (see Whitespaces).
GAP 3.4.4