||Several kinds of semantics for modal logic have been proposed, the most popular of which is Kripke semantics. (This is sometimes called possible worlds semantics, although the formal semantics doesn’t require us to think of the entities in its domain as possible worlds.) In Kripke semantics, models comprise a domain of entities, variously called points, situations, scenarios or possible worlds, with one or more accessible relations between them. The truth-value of a sentence at a possible world w may depend on the truth-value of other sentences at worlds accessible from w. In modal logics, for example, ‘necessarily, A’ is true at a worldw iff A is true at all worlds u accessible from w, and ‘possibly, A’ is true at w iff A is true at some world u accessible from w. This approach can be applied to other kinds of modalities, including ‘agent a knows that’ in modal epistemic logics. One can also give algebraic, topological and categorical semantics for modal logics, in place of Kripke semantics. These approaches have intrinsic mathematical interest, but have received less attention in the philosophical literature (perhaps because they do not provide an analysis of modal concepts in the way that possible worlds semantics does).