(Or "linear analysis", "scanning") The first stage of processing a language.The stream of characters making up the source program or other input is read one at a time and grouped into lexemes (or "tokens") - word-like pieces such as keywords, identifiers, literals and punctutation.The lexemes are then passed to the parser.["Compilers - Principles, Techniques and Tools", by Alfred V. Aho, Ravi Sethi and Jeffrey D. Ullman, pp. 4-5](1995-04-05)