語音組合法

語音組合法(Phonotactics)是語音學的其中一個分支，研究在某一種語言中的語音組合法則。舉例說，在普通話裡，/j/、/q/、及/x/之後只能跟/i/和/ü/，而不能跟/a/、/o/或/e/等韻母；而在英語裡，子音叢集最多只能由兩個子音組成，除非第一個子音是/s/音，則其後可容許符合特殊組合的子音群。在相近的語言，相同的語音組合法則未必相通，例如：在現代英語中，/kn/及/ɡn/在字詞的開首是不容許的，但在同系的德語及荷語中卻是允許的。

語音組合分析

Syllables have the following internal segmental structure:

• Onset (optional)
• Rime (obligatory, comprises Nucleus and Coda):
  • Nucleus (obligatory)
  • Coda (optional)

Both onset and coda may be empty, forming a vowel-only syllable, or alternatively, the nucleus can be occupied by a syllabic consonant.

English phonotactics

主条目：English phonology § Phonotactics

The English syllable (and word) twelfths /twɛlfθs/ is divided into the onset /tw/, the nucleus /ɛ/, and the coda /lfθs/, and it can thus be described as CCVCCCC (C = consonant, V = vowel). On this basis it is possible to form rules for which representations of phoneme classes may fill the cluster. For instance, English allows at most three consonants in an onset, but among native words under standard accents, phonemes in a three-consonantal onset are limited to the following scheme:

/s/ + pulmonic + approximant:

• /s/ + /m/ + /j/
• /s/ + /t/ + /j ɹ/
• /s/ + /p/ + /j ɹ l/
• /s/ + /k/ + /j ɹ l w/

This constraint can be observed in the pronunciation of the word blue: originally, the vowel of blue was identical to the vowel of cue, approximately [iw]. In most dialects of English, [iw] shifted to [juː]. Theoretically, this would produce **[bljuː]. The cluster [blj], however, infringes the constraint for three-consonantal onsets in English. Therefore, the pronunciation has been reduced to [bluː] by elision of the [j].

Other languages don't share the same constraint: compare Spanish pliegue [ˈpljeɣe] or French pluie [plɥi].

Sonority hierarchy

In general, the rules of phonotactics operate around the sonority hierarchy, stipulating that the nucleus has maximal sonority and that sonority decreases as you move away from the nucleus. The voiceless alveolar fricative [s] is lower on the sonority hierarchy than the alveolar lateral approximant [l], so the combination /sl/ is permitted in onsets and /ls/ is permitted in codas, but /ls/ is not allowed in onsets and /sl/ is not allowed in codas. Hence slips /slɪps/ and pulse /pʌls/ are possible English words while *lsips and *pusl are not. There are of course exceptions to this rule, but in general it holds for the phonotactics of most languages.