The present paper analyzes how the semantic and pragmatic functions of closed class categories, or grammatical morphemes (i.e., inflections and function words), organize discourse processing. Grammatical morphemes tend to express a small set of conceptual distinctions that organize a wide range of objects and relations, usually expressed by content or open class words (i.e., nouns and verbs), into situations anchored to a discourse context. Therefore, grammatical morphemes and content words cooperate in guiding the construction of a situation model during discourse (...) comprehension by specifying complementary aspects of described situations. The paper reviews and extends analytical and empirical evidence for this grammatical‐conceptual correspondence, and suggests that the correspondence developed in response to the cognitive demands of discourse processing. Thus the distinction between open and closed linguistic categories is interpreted in terms of a fundamental correspondence between conceptual and linguistic structure that helps organize discourse processing. (shrink)