Talk of the functions of words or concepts has played a central role in conceptual engineering and in other philosophical projects. But what can we mean by ‘functions’ here, and how can we determine what those functions are? Some have expressed skepticism that we can make any good sense of the idea of function as applied to concepts or words. And this is a fair worry to which we ought to be responsive. In this paper I argue that the idea that parts of language (or concepts) have functions is not hopeless, nor are we limited to saying that the function of a concept (or term) F is just ‘to pick out the Fs’. I will try to show how we can get help in understanding and identifying linguistic functions from work in systemic functional linguistics. This in turn enables us to make progress in determining how we should not, and how we should, come to think about function in language, in ways that matter for conceptual engineering and other projects in philosophy.