This paper focuses on the properties of command constructions in Turkish Sign Language (TİD). The nature and function of manual signs and nonmanual markers in command constructions in TİD are investigated to determine their prosodic, morphological, morphophonological, and syntactic properties. We show that TİD does not utilize any of the properties reported in the literature as an obligatory marker of commands in some spoken and sign languages. The only salient marker of commands we have identified is a nonmanual marker: (forward/sideward) head tilt 1 .

Over the history of research on sign languages, much scholarship has highlighted the pervasive presence of signs whose forms relate to their meaning in a non-arbitrary way. The presence of these forms suggests that sign language vocabularies are shaped, at least in part, by a pressure toward maintaining a link between form and meaning in wordforms. We use a vector space approach to test the ways this pressure might shape sign language vocabularies, examining how non-arbitrary forms are distributed within the lexicons of two unrelated sign languages. Vector space models situate the representations of words in a multi-dimensional space where the distance between words indexes their relatedness in meaning. Using phonological information from the vocabularies of American Sign Language (ASL) and British Sign Language (BSL), we tested whether increased similarity between the semantic representations of signs corresponds to increased phonological similarity. The results of the computational analysis showed a significant positive relationship between phonological form and semantic meaning for both sign languages, which was strongest when the sign language lexicons were organized into clusters of semantically related signs. The analysis also revealed variation in the strength of patterns across the form-meaning relationships seen between phonological parameters within each sign language, as well as between the two languages. This shows that while the connection between form and meaning is not entirely language specific, there are cross-linguistic differences in how these mappings are realized for signs in each language, suggesting that arbitrariness as well as cognitive or cultural influences may play a role in how these patterns are realized. The results of this analysis not only contribute to our understanding of the distribution of non-arbitrariness in sign language lexicons, but also demonstrate a new way that computational modeling can be harnessed in lexicon-wide investigations of sign languages.

Polar interrogatives in Turkish Sign Language are marked with a special head movement, HEAD FORWARD. In this study I look at the distribution of this nonmanual marker in the embedded context and show that it is likely not merely a syntactic clause-typer as previously claimed in the literature. My findings reveal that this nonmanual marker's presence and lack thereof distinguish between the semantic types question and proposition, and that it differs from its wh-counterpart, the HEAD BACKWARD, in that it is the sole syntactic clause-typer of the interrogative type, i.e. single conjunct polar, that it marks.