Phonotactic

Phonotactics (from Ancient Greek phōnḗ "voice, sound" and taktikós "having to do with arranging") is a branch of phonology that deals with restrictions in a language on the permissible combinations of phonemes. Phonotactics defines permissible syllable structure, consonant clusters, and vowel sequences by means of phonotactical constraints.

Phonotactic constraints are highly language specific. For example, in Japanese, consonant clusters like /st/ do not occur. Similarly, the clusters /kn/ and /ɡn/ are not permitted at the beginning of a word in Modern English but are in German and Dutch, and were permitted in Old and Middle English. In contrast, in some Slavic languages /l/ and /r/ are used as vowels.

Syllables have the following internal segmental structure:

Both onset and coda may be empty, forming a vowel-only syllable, or alternatively, the nucleus can be occupied by a syllabic consonant. Phonotactics is known to affect second language vocabulary acquisition.

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 (and excluding a few obscure learned words such as sphragistics), phonemes in a three-consonantal onset are limited to the following scheme:

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