Subtheme

noun
1.
a subject of discourse, discussion, meditation, or composition; topic:
The need for world peace was the theme of the meeting.
2.
a unifying or dominant idea, motif, etc., as in a work of art.
3.
a short, informal essay, especially a school composition.
4.
Music.

a principal melodic subject in a musical composition.
a short melodic subject from which variations are developed.

5.
Grammar. the element common to all or most of the forms of an inflectional paradigm, often consisting of a root with certain formative elements or modifications.
Compare stem1 (def 16).
6.
Linguistics. topic (def 4).
7.
Also, thema. an administrative division of the Byzantine Empire.
adjective
8.
having a unifying theme:
a theme restaurant decorated like a spaceship.
verb (used with object), themed, theming.
9.
to provide with a theme.
noun
1.
an idea or topic expanded in a discourse, discussion, etc
2.
(in literature, music, art, etc) a unifying idea, image, or motif, repeated or developed throughout a work
3.
(music) a group of notes forming a recognizable melodic unit, often used as the basis of the musical material in a composition
4.
a short essay, esp one set as an exercise for a student
5.
(linguistics) the first major constituent of a sentence, usually but not necessarily the subject. In the sentence history I do like, “history” is the theme of the sentence, even though it is the object of the verb
6.
(grammar) another word for root1 (sense 9), stem1 (sense 9)
7.
(in the Byzantine Empire) a territorial unit consisting of several provinces under a military commander
8.
(modifier) planned or designed round one unifying subject, image, etc: a theme holiday
verb
9.
(transitive) to design, decorate, arrange, etc, in accordance with a theme

theme definition

A central idea in a piece of writing or other work of art: “The theme of desperation is found throughout his novels.” Also a short composition assigned to a student as a writing exercise.