This chapter presents the semantics and pragmatics of prosodic focus in alternative semantics. Half a dozen examples are given of empirical phenomena that are to be covered by the theory. Then a syntax marking the locus, scope, and antecedent for focus is introduced. The syntax is interpreted semantically and pragmatically by a presupposition involving alternatives. The alternative sets that are used in the definition are computed compositionally using a recursive definition. Alternatives are also employed in the semantics of questions, and this ties in with the phenomenon of question-answer congruence, where the position of focus in an answer matches questioned positions in the question. A different semantic interpretation for focus is entailment semantics, which uses a generalized entailment condition in place of a condition involving alternatives. The semantic and pragmatic interpretation for contrastive topic uses an additional layer of alternatives. Independent of focus, alternatives are deployed in the semantics of disjunction and of negative polarity items. Author's preprint.