This paper presents some basic principles in the structuring of polysemous lexical categories. On the basis of several Croatian lexical categories belonging to different word classes, the author analyses principles relevant for the structuring of nouns, adjectives and verbs. The existence of a structurally stable part of a lexeme is suggested, which enables the formation of conceptual innovations as distinct lexical senses. The structurally stable part of a lexical category could be seen as the typical meaning or as a schematic concept. Conceptual innovations could be interpreted as a result of metaphoric or metonymic extensions or as examples of a schematic concept. The paper tries to describe how these modes are related and what their role is in the semantic structuring of lexical categories.