thematic

Etymology

From Ancient Greek θεματικός (thematikós), from θέμα (théma, “theme”). Equivalent to theme + -atic.

adj

1. Relating to, or having a theme (“subject”) or a topic.
   He had a thematic collection of postage stamps with flags on them (where (UK) thematic collection is equivalent to (US) topical collection)
2. (music) Relating to a melodic subject.
3. (grammar) Of a word stem, ending in a vowel that appears in or otherwise influences the noun or verb's inflection.
   A considerable number of derived nominals, especially thematic nouns, also exhibited o-grade roots. 2006, Donald Ringe, From Proto-Indo-European to Proto-Germanic (A Linguistic History of English; 1), Oxford: Oxford University Press, page 12
4. (history) Of or relating to a theme (“subdivision of the Byzantine empire”).

noun

1. A postage stamp that is part of a thematic collection.