motif

A motif is a design or an idea that keeps returning through a work. You notice it the third time.

Music uses it precisely, since a motif is a short recurring musical figure, and the four notes at the start of Beethoven's fifth are the most famous example in the world. Literature uses it for a recurring image or theme. Textiles and wallpaper use it for a repeated pattern. The word came from French and shares a root with motive, both from the idea of movement. It is pronounced with the stress on the second syllable.