This section further sharpens our understanding about vowels within syllable structure. The widely observed fact that the ``short'' vowels cannot occur in stressed, unchecked syllables amounts to the restriction that if the syllable contains a short vowel, a coda must be present. -1z The converse point is also justified by observation. The long mid and high vowels can occur with following /r/ in the same syllable as well as with /r/ in a subsequent syllable, as in Table above. Further, these vowels may may precede /r/ and other consonants simultaneously: fierce, fort,3.35 etc. A coda is not necessary after a long vowel (as in see, say, sigh, Sue, sew, sow, soy3.36). Representing length by the presence of a glide position, we may put these two observations into a single sentence: Stressed syllables must include a coda or a glide. We may even omit the disjunction and reduce it further, as in (6).
(6) Stressed rhymes branch.
If a branching rhyme is understood as a rhyme with a branch anywhere within it, then this statement holds equally under syllable structures (b), (c), or (d).
Syllable weight may be defined as branching structure within the rhyme, so that morae -- the units of syllable weight -- may be counted by counting the branches within the rhyme and adding one. Then, stress is attracted to heavy syllables. Many languages make a similar distinction between heavy and light syllables, in which stressed syllables must be heavy.3.37
This section presented a number of classes of vowel length and complexity, attributing some distinctions to phonetic and suprasyllabic factors, and others to the phonological structure of the syllable. The distributional pattern of ``short'' vs. ``long'' vowels is explained by the constraint, Stressed rhymes branch. The low diphthongs were argued to be ``longer'' even than the ``long'' vowels because they don't allow following /r/ in the same syllable. An exemplar of pregenerative English vowel theory in which /r/ follows glides within the syllable was examined and its catalog of counterexamples to the theory that /r/ is a glide was systematically destroyed. We conclude with a theory of the temporal structure of vowels: A vowel consists of a nucleus followed in some cases by a glide. If structure (b) above is assumed, then the concept, ``vowel'', may be defined as the constituent containing the nucleus and the glide, there labelled nuc'. This may be reduced to the context-free-grammar rewrite rule in (7).
(7) Vowel 14#14 Nucleus (Glide)
This rule, characterizing part of English syllable structure, provides a formal, technical definition of ``English vowel''.