 To say that propositions are structured is to say something about the nature of propositions. Roughly, to say that propositions are structured is to say that they are complex entities, entities having parts or constituents, where the constituents are bound together in a certain way. Thus, particular accounts of structured propositions can (and do) differ in at least two ways: 1) they can differ as to what sorts of things are the constituents of structured propositions; and 2) they can differ as to what binds these constituents together in a proposition. Various accounts of structured propositions that differ in these ways will be discussed below.