A subject, now especially of a talk or an artistic piece; a topic.

A recurring idea or motif, or a concept with multiple instantiations, or a color palette or skin that affects the visuals and other elements of a design or app.

(music) The main melody of a piece of music, especially one that is the source of variations.

(film, television) A song, or a snippet of a song, that identifies a film, a TV program, a character, etc. by playing at the appropriate time.

(grammar) The stem of a word.

(linguistics) thematic relation of a noun phrase to a verb.

(linguistics) Theta role in generative grammar and government and binding theory.

(linguistics) Topic, what is generally being talked about, as opposed to rheme.

A regional unit of organisation in the Byzantine empire.

(transitive) To give a theme to.

(computing, transitive) To apply a theme to; to change the visual appearance and/or layout of (software).