couplet

In literature, a pair of lines of verse, which usually rhyme and are of the same length.

The heroic couplet, consisting of two rhymed lines in iambic pentameter, was widely adopted for epic poetry, and was a convention of both serious and mock-heroic 18th-century English poetry, as in the work of Alexander Pope. An example, from Pope's ‘An Essay on Criticism’, is: ‘A little learning is a dang'rous thing;/Drink deep, or taste not the Pierian spring.’

couplet

A verse or stanza in a poem. In music, a strophic song, generally of a light and often of a humorous type, in which the same music recurs for each verse. Also the forerunner of the episode in the rondo form, occurring in the French rondeau as cultivated by Couperin and others, where a main theme returns again and again after statements of various couplets between.