Irreversible binomial

In linguistics and stylistics, an irreversible binomial, frozen binomial, binomial freeze, binomial expression, binomial pair, or nonreversible word pair is a pair of words used together in fixed order as an idiomatic expression or collocation. The words have a semantic relationship usually involving the words and or or. They also belong to the same part of speech: nouns (milk and honey), adjectives (short and sweet), or verbs (do or die).