Merism

Merism is a literary and rhetorical device that involves the use of two contrasting or opposite terms to refer to a whole or a more extensive concept. It's a way of expressing a complete idea by highlighting extremes, often implying everything in between. For example, phrases like "sink or swim" or "the rich and the poor" encompass a broader spectrum than just the two elements mentioned. In literature and poetry, merism can be used to create emphasis, portray completeness, or evoke imagery.