Constituents of the syllable

The universal syllable template accepted by most phonologists is given in (1). Note that small sigma (σ) is shorthand for ‘syllable’; capital sigma (Σ), as we shall see later, is used to symbolize the foot.

The only compulsory part of the syllable, and hence its head, or most important, defining unit, is the nucleus. This will generally contain a vowel (and recall that vowels are [+syllabic]): indeed, the syllable I, or the first syllable of about, consist only of a nucleus. If no vowel is available, certain consonants can become nuclear, and play the part of a vowel. In English, this is true of /l/, /m/, /n/, and /r/ in rhotic accents: that is, the sonorant consonants, in natural class terms. Each of the words bottle, bottom, button, butter has two syllables, and in each case, the second syllable consists only of nuclear, or syllabic .

Both the onset and the coda are optional constituents, and each, if filled, will contain one or more consonants. In English, be has an onset but no coda; eat has a coda but no onset; and beat has both. Recognizing the difference between the nucleus, which is primarily the domain of vowels, and the onset and coda, where we find consonants, also casts some light on the relationship between the high vowels /i u/ and the glides /j w/. Phonetically, it is very hard to detect any systematic difference between [i] and [j], or [u] and [w] respectively; however, we can now say that [i] and [u] are [+syllabic], while the glides are [–syllabic], so that in ye, [j] is in the onset and [i:] in the nucleus, and similarly in woo, [w] is an onset consonant and [u:] a nuclear vowel. Clearly, [j] and [i:] are extremely similar phonetically; furthermore, since distinguishing syllable peaks, or nuclei, from margins allows us to predict where each will occur, they are in complementary distribution (and the same is true of [w] and [u:]). This makes [j] and [i:], and [w] and [u:], allophones of a single phoneme, with their distribution determined by position in the syllable.