theme

noun

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

   “"Had not you once a beautiful daughter, named Mary?" said the stranger. "It is a heartrending question, man," said Andrew; "but certes, I had once a beloved daughter named Mary." "What became of her?" asked the stranger. Andrew shook his head, turned round, and began to move away; it was a theme that his heart could not brook.”

2. A recurring idea; a motif.

   “variations on the theme of entrepreneurial resourcefulness”

3. A recurring idea; a motif.

   “switch to a dark theme to conserve battery power”

4. (dated)An essay written for school.

   “Father Dolan came in today and pandied me because I was not writing my theme.”

   “[…] his themes and exercises were in constant demand for what we called cogging and American students rather grandly called plagiarization.”

5. The main melody of a piece of music, especially one that is the source of variations.
6. A song, or a snippet of a song, that identifies a film, a TV program, a character, etc. by playing at the appropriate time.
7. An additional puzzle within the crossword, typically involving a set of non-standard clues or answers.
8. The stem of a word.
9. Thematic relation of a noun phrase to a verb.
10. Theta role in generative grammar and government and binding theory.
11. Topic, what is generally being talked about.
12. A regional unit of organisation in the Byzantine empire.

verb

1. (transitive)To give a theme to.

   “We themed the birthday party around superheroes.”

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