van Dooren, AnnemarieIn this dissertation I investigate the syntax and semantics of modals like can and must and their counterparts in other languages. Modals like can and must can be used to express both obligations (as in employees must wash their hands, called deontic modality) and possibilities given what is known (as in John must be home; his car isn't in the parking lot, called epistemic modality), but previous work shows that the availability of these different 'flavors' of modality are constrained by their syntactic environment. My main claim is that in all languages discussed, modal meanings are specifically restricted by their complement size. For English modals, which are treated as functional items that are part of the functional projections from the verb, this is often captured by having modals appear in different positions in the functional projection of the verb based on their modal flavor: Epistemic modals are located high, above tense, while non-epistemic modals, such as deontics, are located low, below aspect (Cinque 1999, Hacquard 2006, 2008, a.o.). I argue that in Dutch, modals are verbs (following Aelbrecht 2010), and as such, they host their own functional projections. Despite this, some of the same syntactic restrictions on the availability of modal flavor hold, which argues for a recasting of the cross-linguistic generalizations not in terms of position of the functional projection, but in terms of complement size. I claim that cross-linguistically, different flavors require different types of complements: epistemics need a complement the size of a Tense Phrase (in line with Cinque 1999, Hacquard 2006), deontics need the size of an Aspectual Phrase (building on Rubinstein 2012), while other non-epistemics can combine with a smaller-sized complement. I will provide two case studies in favor of the claim that complement size restricts the availability of modal flavors: In chapter 3, I will discuss the interaction between tense and modality, and in chapter 4, I will discuss the case of modals with non-verbal complements.enDissertationLinguisticsDutchmodalitysemanticssyntax