This chapter surveys the expression of modality and mood in American Sign Language (ASL), with a focus on modality and, specifically, modal verbs. Beyond sentence types, mood has not been explored extensively for ASL to date, although recent work on irrealis moods has been fruitful. For a signed language such as ASL, articulation with the hands is accompanied by distinctive facial gestures and body/head postures, which become increasingly important as epistemic readings of modals are obtained. Here we give a detailed discussion of modals in ASL that range from agent-oriented to epistemic, looking at both form and function, including some negative modals. We trace the grammaticalization of a number of modal categories and show how at least some of these categories have grammaticalized from earlier gestural sources. Regarding mood, we include some discussion of conditionals, hypotheticals, and counterfactuals.
