In poetry, what term refers to a turn of thought or argument, particularly in a sonnet?

The term that refers to a turn of thought or argument in poetry, particularly in a sonnet, is indeed "volta." In many traditional sonnets, the volta typically appears at the ninth line, marking a shift in the theme or argument of the poem. This shift can present a contrast, offer a resolution, or introduce a new perspective on the theme addressed in the earlier parts of the poem. The ability to recognize the volta helps readers understand the development of ideas and emotions within the sonnet's structure.

Antithesis involves the juxtaposition of contrasting ideas, but it does not specifically denote a turn of thought; it's more about highlighting differences. A couplet is a two-line stanza or a pair of lines that usually rhyme, but it doesn’t inherently convey a thematic shift. Rhyme scheme refers to the pattern of rhymes at the end of each line; while important in poetry, it doesn’t pertain to the concept of a turn in thought or argument. Thus, understanding the role of the volta is crucial in analyzing the overall message and progression of a sonnet.