What is meant by a 'language' is actually fairly well defined mathematically: That is something that can be described by a number of grammars. These in turn can

What is meant by a 'language' is actually fairly well defined mathematically: That is something that can be described by a number of grammars. These in turn can be categorised (see the Chomsky Hierarchy: http://en.wikipedia.org/wiki/Chomsky_hierarchy http://en.wikipedia.org/wiki/Chomsky_hierarchy) In that sense, programming languages, regular expressions, and natural language can all be identified by what types of grammar can define them.