A couplet is a pair of successive lines of verse, usually linked by rhyme and often forming a complete syntactic and thematic unit. The couplet is one of the smallest structural units in poetry — two lines — yet it can function as a self-contained poem, a stanza form, or a closing gesture.
The heroic couplet — two rhyming lines of iambic pentameter — was the dominant form in English poetry from the Restoration through the eighteenth century (Dryden, Pope). It favors balance, antithesis, and wit: each line answers the other, and the rhyme snaps the thought shut.
In the Shakespearean sonnet, the final couplet delivers the volta — a resolution, reversal, or summation that reframes everything that came before. The couplet’s closure gives it epigrammatic force: it is the form of the last word.