Language

There are many different types of language. One type with which we are familiar are formal languages, such as those defined by BNF. Formal languages are widely used in computer science, mainly because of their precise definition and unambiguity.

Human languages fundamentally differ from formal languages. Human language, often called "natural" language, is ambiguous. In fact, ambiguities are central to the use of human language, as they permit people to express many different shades of meaning, and to be able to convey a range of meanings at once.

Most of the work on modeling human language in machines centers on extending the basic paradigm of formal languages to include natural language.

• Strings such as "Your goose is cooked." are made up of terminal symbols - "Your", "goose", "is", "cooked".

• The phrase structure of strings is composed of phrases. For example, a sentence may be composed of a noun phrase followed by a verb phrase.

• This structure is embodied in rewrite rules: S --> NP VP.