Grammar. (of a word or words) of, relating to, or producing a theme or themes. (of a vowel) pertaining to the theme or stem: the thematic vowel ends the stem and precedes the inflectional ending of a word form, as i in Latin audiō “I hear.”.
of, relating to, or consisting of a theme or themes
(linguistics) denoting a word that is the theme of a sentence
(grammar) denoting a vowel or other sound or sequence of sounds that occurs between the root of a word and any inflectional or derivational suffixes of or relating to the stem or root of a word