In poetry, what is a group of lines that functions similarly to a paragraph called?

The correct term for a group of lines in poetry that functions like a paragraph is "stanza." A stanza serves as a structural unit within a poem, grouping together several lines that often share a common theme or idea. This organization enhances the flow and coherence of the poem, much like paragraphs do in prose. Each stanza might vary in length and can contain various rhyme schemes or rhythms, providing a framework that helps convey the poet's message.

The other choices refer to specific poetic forms or concepts but do not encompass the broader idea of grouping lines. "Verse" typically refers to any single line of poetry or more generally to poetry itself and does not specify a grouping structure. A "couplet" is specifically a pair of lines that usually rhyme and is quite short, while a "quatrain" is a four-line stanza. While both couplets and quatrains are types of stanzas, they are not the general term for any group of lines, which is what is being asked in this question.