Language contact is the process by which two languages influence each other.

Pidginization is the process by which a new language develops out of the contact between two or more languages, while borrowing, code-switching, and calque are all types of language contact.

A loanword is a word or phrase that is borrowed from another language.

A calque is a word or phrase that is borrowed from another language and translated literally.

Code-switching is a situation in which two languages are used interchangeably by a speaker.

Tok Pisin is a pidgin language that is spoken in Papua New Guinea.

A creole is a language that develops out of a pidgin language.

Haitian Creole is a creole language that is spoken in Haiti.

Diglossia is a situation in which one language is dominant over another in a society.

The use of Standard English and African American Vernacular English in the United States is an example of a diglossic situation.

Language shift is a situation in which a language is replaced by another language in a society.

The decline of the Irish language in Ireland is an example of a language shift.

Language revitalization is a situation in which a language is revived or revitalized.

The revival of the Hawaiian language in Hawaii is an example of a language revitalization effort.

Language maintenance is a situation in which a language is maintained or preserved in a society.

The use of Irish in schools in Ireland is an example of a language maintenance effort.