Languages in Contact
The main topics in this field are:
1. pidgin and creole languages,
2. lingua francas and trade languages,
3. borrowing and semantic shift,
4. linguacide.
It is related to bilingualism, language change and borrowing, dialectalization, and many other phenomena. Some people think English and many other 'natural' languages are really creoles. Derek Bickerton's hypothesis that a) child language acquisition, b) creolization, and c) origination of language have similar properties is one of the most powerful, interesting, and controversial ideas in linguistics.