In this paper, I make a case for interpreting the Lysis as a dialogue of definition, designed to answer the question of “What is a friend?” The main innovation of my interpretation is the contention – and this is argued for in the paper – that Socrates hints towards a definition of being a friend that applies equally to mutual friendship and one-way attraction – the two kinds of friend relation very clearly identified by Socrates in the dialogue. The key (...) to understanding how the two different kinds of friendship can have a common definition is to appreciate that the property of being a friend has a relational character. (shrink)