Adapting tools recently developed in general linguistics and dwelling on a solid corpus study, this book offers the first comprehensive view on Classical Greek wh-clauses since Monteil (1963) and scrutinizes how wh-items (ὅς, ὅστις, τίς) distribute across the different clause types. False ideas are discarded (e.g., there are no τίς relative clauses, ὅστις does not take over ὅς’ functions). This essay furthermore teases apart actual neutralization and so-far-unknown subtle distinctions. Who knew that ὅστις is featured in three different types of appositive clauses? In the interrogative domain, an analysis is given of what licenses ὅς to pop in and τίς to pop out. Tackling these topics and more, this essay draws a coherent picture of the wh-clause system, whose basis is the notion of (non)identification.