Meaning of “theme” - Learner’s Dictionary

theme

noun us uk /θiːm/

B2 [ C ] the subject of a book, film, speech, etc:

The theme of loss runs through most of his novels.

More examples

theme music/song/tune

the music that is played at the beginning and end of a particular television or radio programme

(Definition of “theme” from the Cambridge Learner’s Dictionary © Cambridge University Press)