One of Wittgenstein's best-known and most important philosophical contributions in the Philosophical Investigations is his account of the 'family resemblance' character of general concepts. The chapter provides a brief description of Wittgenstein's conception of 'family resemblance' as a characteristic of concepts. It distinguishes that characteristic from various others with which it has commonly been confused. The chapter discusses Wittgenstein's views concerning the philosophical significance of the existence of such concepts, in particular, its refutation of a certain sort of Platonism; its bearing on his own position that concepts are constituted by rules which govern the use of words; and its role in diagnosing and dispelling a broad range of philosophical illusions. The chapter defuses some residual problems which may seem to afflict Wittgenstein's notion of family resemblance concepts. Finally, it discusses one important issue concerning reductionism.