top·ic 
(t
ŏp
ĭk)
n.1. The subject of a speech, essay, thesis, or discourse.
2. A subject of discussion or conversation.
3. A subdivision of a theme, thesis, or outline. See Synonyms at subject.
4. Linguistics A word or phrase in a sentence, usually providing information from previous discourse or shared knowledge, that the rest of the sentence elaborates or comments on. Also called theme.
[Obsolete topic, rhetorical argument, sing. of Topics, title of a work by Aristotle, from Latin Topica, from Greek Topika, commonplaces, from neuter pl. of topikos, of a place, from topos, place.]