 This article divides philosophical discussions of natural kinds into four areas: metaphysics, epistemology, philosophy of science, and philosophy of language. The metaphysics of natural kinds asks whether we should think of our supposed natural kinds as genuinely natural. And if they are, what are natural kinds? And, finally, do natural kinds have essences? Philosophy of science is concerned with natural kinds because, as mentioned above, it is the use of natural kinds by the individual (‘special’) sciences that generates our interest in them. So we may ask, whether the kinds appearing in our best scientific theories do indeed satisfy the theories of natural kinds proposed by the metaphysicians. Philosophy of language takes an interest in natural kinds because basic issues are raised by the semantics of natural kind terms. For example, if we think of naming an entity and describing it as, semantically speaking, fundamentally different ways of talking about it, should we think of natural kind terms as functioning like names or like descriptions?