In the linguistic literature, the term theme has several interpretations, one of which relates to discourse analysis and two others to sentence structure. In a more general (or global) sense, one may speak about the theme or topic (or topics) of a text (or discourse), that is, to analyze relations going beyond the sentence boundary and try to identify some characteristic subject(s) for the text (discourse) as a whole. This analysis is mostly a matter of the domain of information retrieval and only partially takes into account linguistically based considerations. The main linguistically based usage of the term theme concerns relations within the sentence. Theme is understood to be one of the (syntactico-) semantic relations and is used as the label of one of the arguments of the verb; the whole network of these relations is called thematic relations or roles (or, in the terminology of Chomskyan generative theory, theta roles and theta grids). Alternatively, from the point of view of the communicative function of the language reflected in the information structure of the sentence, the theme (or topic) of a sentence is distinguished from the rest of it (rheme, or focus, as the case may be) and attention is paid to the semantic consequences of the dichotomy (especially in relation to presuppositions and negation) and its realization (morphological, syntactic, prosodic) in the surface shape of the sentence. In some approaches to morphosyntactic analysis the term theme is also used referring to the part of the word to which inflections are added, especially composed of the root and an added vowel.
