In phonology, minimal pairs are pairs of words or phrases in a particular language, spoken or signed, that differ in only one phonological element, such as a phoneme, toneme or chroneme, and have distinct meanings. They are used to demonstrate that two phones represent two separate phonemes in the language.
Many phonologists in the middle part of the 20th century had a strong interest in developing techniques for discovering the phonemes of unknown languages, and in some cases, they set up writing systems for the languages. The major work of Kenneth Pike on the subject is Phonemics: a technique for reducing languages to writing. The minimal pair was an essential tool in the discovery process and was found by substitution or commutation tests.
As an example for English vowels, the pair "let" + "lit" can be used to demonstrate that the phones [ɛ] (in let) and [ɪ] (in lit) actually represent distinct phonemes /ɛ/ and /ɪ/. An example for English consonants is the minimal pair of "pat" +