Hook [hoo-k] (music)  a musical idea, often a short riff, passage, or phrase, that is used in popular music to make a song appealing and to “catch the ear of the listener”. The term generally applies to popular music, especially rock music, R&B, hip hop, dance music, and pop. In these genres, the hook is often found in, or consists of, the chorus. A hook can be either melodic or rhythmic, and often incorporates the main motif for a piece of music.  used in the plural form, a term describing the music and melodies of Mikal Cronin, often resulting in day-long-episodes of humming and spasmodic fits of inadvertent chorus singing (see also Hooks for Days and Days and Melodies That Just Won’t Quit.)
Examples listed below.