Definition of theme:
the subject matter of a conversation or discussion; "he didn't want to discuss that subject"; "it was a very sensitive topic"; "his letters were always on the theme of love"
a unifying idea that is a recurrent element in literary or artistic work; "it was the usual `boy gets girl' theme"
(music) melodic subject of a musical composition; "the theme is announced in the first measures"; "the accompanist picked up the idea and elaborated it"
an essay (especially one written as an assignment); "he got an A on his composition"
(linguistics) the form of a word after all affixes are removed; "thematic vowels are part of the stem"
provide with a particular theme or motive; "the restaurant often themes its menus"