The field of syntactic study focuses on the rules and principles governing the possible surface and abstract functional relations between words (and in non-lexicalist theories, parts of words) in constituting grammatical sentences or phrases in a given language, and in Language more generally.
Due to the fairly fixed word order of English, a central concern in modern Western syntax has been the rules governing surface word order, and the relation between the underlying functional structure of a clause or phrase and its surface structure. In contrast, the Indian tradition has little to say on questions of word order (certainly in regard to the relative ordering of major clausal constituents), reflecting the highly flexible word order of Sanskrit.
Perhaps the most important, and best known, contribution of the Indian tradition to the study of syntax is in relation to the theory of argument structure, that is of the rules governing the grammatical realization of the semantic arguments of predicates. But the Indian tradition addresses many other important syntactic issues. These are often in connection with morphological or semantic issues, but certain texts, such as those of the samanvaya tradition, deal directly with specifically syntactic topics.