In this thesis, we offer an account of the mutual constraints on the levels of morphology, syntax, phonology, semantics and pragmatics in Turkish. We analyse the interpretive aspects of Turkish case morphology, syntax and phonology in terms of notions like strongness, focus, topic and predication. In elaborating and formulating these notions, we mainly rely on situation-theoretic ideas and tools. We start by examining the semantics of the (Turkish) accusative suffix. We show that a direct object in Turkish must carry this suffix if it receives one of the interpretations which are usually categorised as strong (namely definite, partitive, (epistemically) specific or strongly quantified interpretations). Based on our discussion about accusative morphology, we later on offer a unified account of the semantics of case morphology in Turkish. We also offer an analysis of variations in word order and phonology in Turkish in terms of focus-background and topic-comment. We argue that there are (at least) three different notions of focus (and also of background) that should be identified and kept apart in the analysis of sentence structure: focus of association, focus of assertion, and focus of description. We claim that the topic-comment articulation is a pragmatically motivated instance of predication, where the topic is the subject of predication and the comment is the predicate. After a discussion of topic-comment, we propose a general semantic analysis of predication. Case marking and definiteness marking in Turkish are two other phenomena which we investigate in this thesis. We propose some principles that formulate the strategies employed in Turkish for case assignment and definiteness marking. We conclude our analysis with an HPSG grammar that brings together and formalise our major findings.