HEMISTICH:The approximate half of a line of poetic verse. In dramatic poetry, where the hemistichs are split into two short lines, it is used whenever characters exchange short bursts of dialogue rapidly, heightening the effect of quarrelsome disagreement; in classical poetry such a series is called hemistichomythia. Other types of poetry may use an occasional hemistich to give the effect of emotionally disturbed thought or action.
at left, Richard Wilbur