In this course, we ask the question: how can sign languages inform our understanding of grammar? Sign languages are, on a par with spoken languages, instantiations of universal grammar, but they use the visual-gestural modality. Investigating their properties can thus reveal aspects of grammar which remain unobservable in the oral signal, due to articulatory constraints and other limitations relative to the linearity of speech. Furthermore, a better understanding of sign languages and of their commonalities with spoken languages also helps determine what in the linguistic signal (oral or visual) is contingent upon the physical limitations imposed by the medium, and what is an expression of the essential properties of language cognition. The course will cover a selection of phenomena (in phonology, syntax and semantics) that are important for understanding the structure of sign languages.