the subject matter of a conversation or discussion

something (a person or object or scene) selected by an artist or photographer for graphic representation

a branch of knowledge

some situation or event that is thought about

(grammar) one of the two main constituents of a sentence; the grammatical constituent about which something is predicated

a person who is subjected to experimental or other observational procedures; someone who is an object of investigation

a person who owes allegiance to that nation

(logic) the first term of a proposition