It is proposed that concepts contain two types of properties. Context-independent properties are activated by the word for a concept on all occasions. The activation of these properties is unaffected by contextual relevance. Context-dependent properties are not activated by the respective word independent of context. Rather, these properties are activated only by relevant contexts in which the word appears. Context-independent properties form the core meanings of words, whereas context-dependent properties are a source of semantic encoding variability. This proposal lies between two opposing theories of meaning, one that argues all properties of a concept are active on all occasions and another that argues the active properties are completely determined by context. The existence of context-independent and context-dependent properties is demonstrated in two experimental settings: the property-verification task and judgments of similarity. The relevance of these property types to cross-classification, problem solving, metaphor and sentence comprehension, and the semantic-episodic distinction is discussed.