theme

noun

1.
the subject matter of a conversation or discussion
Derived from:
thematic
2.
a unifying idea that is a recurrent element in literary or artistic work
Derived from:
thematic
3.
(music) melodic subject of a musical composition
Derived from:
thematic
4.
an essay (especially one written as an assignment)
5.
(linguistics) the form of a word after all affixes are removed