According to epistemological contextualism, a sentence of the form "S knows that p" doesn't express a complete proposition. Different utterances of the sentence, in different contexts, can express different propositions: "know" is context-dependent. This paper deals with the semantic contextualist thesis grounding epistemological contextualism. We examine various kinds of linguistic context dependence, which could be relevant to epistemological contextualism: ambiguity, ellipsis, indexicality, vagueness of scalar predicates, dependence on standards of precision. We argue that only an accurate analysis of the different varieties of context sensitivity secures us a better understanding and a clearer evaluation of the contextualist approach.