onset

The syllable serves a number of important functions in phonological theory and practice. The most basic function is to regulate the ways in which lower-level units, including consonants and vowels (as well as the features and gestures), in the phonological hierarchy can legally combine. The rules that govern the legal combinations of segments (consonants and vowels) are called the phonotactic rules, or morpheme structure conditions. Since the syllable is the principal structure which determines these legal combinations (i.e., well-formedness), we say that the syllable is the basic phonotactic unit. In articulatory phonology, the syllable is also used as the unit to organize the ways in which various gestures are allowed to overlap among each other. Therefore, in this view, much of coarticulation is organized around the syllable structure.