A general definition of language must cover a variety of distinct categories: natural languages, programming languages, mathematical languages, etc. The notion of natural languages like English, Hindi, etc. is familiar to us. Informally, language can be defined as a system suitable for expression of certain ideas, facts, or concepts, which includes a set of symbols and rules to manipulate these. The languages we consider for our discussion is an abstraction of natural languages. That is, our focus here is on formal languages that need precise and formal definitions. Programming languages belong to this category. We start with some basic concepts and definitions required in this regard.

Symbols :

Symbols are indivisible objects or entity that cannot be defined. That is, symbols are the atoms of the world of languages. A symbol is any single object such as , a, 0, 1, #, begin, or do. Usually, characters from a typical keyboard are only used as symbols.