theme vs treatise

theme

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

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

  • The stem of a word. 

  • A concept with multiple instantiations. 

  • Topic, what is generally being talked about, as opposed to rheme. 

  • A regional unit of organisation in the Byzantine empire. 

  • thematic relation of a noun phrase to a verb. 

  • Theta role in generative grammar and government and binding theory. 

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

  • Any of various colors, or color palettes, in which a design is offered; (graphical user interface) any of various skins for an app, affecting the visuals and perhaps other elements such as sound effects. 

verb
  • To give a theme to. 

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

treatise

noun
  • A formal, usually lengthy, systematic discourse on some subject. 

How often have the words theme and treatise occurred in a corpus of books? (source: Google Ngram Viewer )