The idea that the concept ‘knowledge’ has a distinctive function or social role is increasingly influential within contemporary epistemology. Perhaps the best-known account of the function of ‘knowledge’ is that developed in Edward Craig's Knowledge and the State of Nature (1990, Oxford University Press), on which (roughly) ‘knowledge’ has the function of identifying good informants. Craig's account of the function of ‘knowledge’ has been appealed to in support of a variety of views, and in this paper I'm concerned with the claim that it supports a sort of epistemic contextualism, which is (roughly) the view that the semantic contents and truth-conditions of ‘knowledge’ ascriptions – instances of ‘S knows that p’ – depend on and vary with the context of ascription (see, for instance, John Greco's ‘What's wrong with contextualism’, Philosophical Quarterly [2008]). Prima facie, this claim should strike us as surprising. A number of concepts and linguistic items (words, sentences) serve functions that have little or nothing to do with semantics. However, I argue that, on the best interpretation of talk of the function of a concept such as ‘knowledge’, the function of ‘knowledge’ is relevant to semantics. Along the way I also suggest how to improve on what I call the ‘usual argument’ that Craig's account of the function of ‘knowledge’ supports epistemic contextualism.