Deponency is a mismatch between form and function in language that was first described for Latin, where there is a group of verbs (the deponents) which are morphologically passive but syntactically active. This is evidence of a larger problem involving the interface between syntax and morphology: inflectional morphology is supposed to specify syntactic function, but sometimes it sends out the wrong signal. Although the problem is as old as the Western linguistic tradition, no generally accepted account of it has yet been given, and it is safe to say that all current theories of language have been constructed as if deponency did not exist.