What is a regularly repeated line or group of lines in a poem or song called?

A regularly repeated line or group of lines in a poem or song is referred to as a refrain. This term captures the essence of repetition, which serves to emphasize certain emotions, themes, or ideas throughout the piece. Refrains help create a rhythm that enhances the overall impact of the work, often making it more memorable for the audience. This technique is commonly found in both poetry and music, reinforcing key phrases or sentiments each time they appear.

In contrast, other terms like verse and stanza refer to structural elements of poems or song lyrics but do not specifically denote repetition. A verse typically refers to a single line or a set of lines within a poem, and a stanza is a grouped set of lines that form a subdivision within a poem, similar to a paragraph in prose. A chorus, while also a repeated section in a song, usually contains the main theme or musical hook, but it is distinct from a refrain, which can appear between verses or at various times throughout a poem or song without necessarily being the title theme.