A double negative is a construction occurring when two forms of grammatical negation are used in the same sentence. This is typically used to convey a different shade of meaning from a strictly positive sentence ("You're not unattractive" vs "You're attractive"). Multiple negation is the more general term referring to the occurrence of more than one negative in a clause. In some languages, double negatives cancel one another and produce an affirmative; in other languages, doubled negatives intensify the negation. Languages where multiple negatives affirm each other are said to have negative concord or emphatic negation. Portuguese, Persian, French, Russian,
Polish,
Bulgarian,
Greek, Spanish, Old English, Italian, Afrikaans, Hebrew are examples of negative-concord languages. This is also true of many vernacular dialects of modern English. Chinese, Latin, German, Dutch, Japanese, Swedish and modern Standard English are examples of languages that do not have negative concord. Typologically, negative concord occurs in a minority of languages.
Languages without negative concord typically have negative polarity items that are used in place of additional negatives when another negating word already occurs. Examples are "ever", "anything" and "anyone" in the sentence "I haven't ever owed anything to anyone" (cf. "I haven't never owed nothing to no one" in negative-concord dialects of English, and "Nunca devi nada a ninguém" in Portuguese, lit. "Never have I owed nothing to no one", or "Non ho mai dovuto nulla a nessuno" in Italian). Negative polarity can be triggered not only by direct negatives such as "not" or "never", but also by words such as "doubt" or "hardly" ("I doubt he has ever owed anything to anyone" or "He has hardly ever owed anything to anyone").
Because standard English does not have negative concord but many varieties and registers of English do, and because most English speakers can speak or comprehend across varieties and registers, double negatives as collocations are functionally auto-antonymic (contranymic) in English; for example, a collocation such as "ain't nothin" or "not nothing" can mean either "something" or "nothing", and its disambiguation is resolved via the contexts of register, variety, location, and content of ideas.