Theta Role (definition)

A concept in generative grammar, which is representative of the arguments required by different types of verbs. Different verbs, IE: transitive, instranstive,ditransitive, etc require subjects, or subjects and objects,or subjects, objects, and indirect objects, and so on. Each of these arguments has a designated theta role which specifies its particular semantic relation to the verb and to other words in the sentence. Examples of theta roles include: agent, experiencer, goal, source, etc.