Phoneme

In oral language, a phoneme is the theoretical basic unit of sound that can be used to distinguish words or morphemes; in sign language, it is a similarly basic unit of hand shape, motion, position, or facial expression. (Formerly termed chereme.) That is, changing a phoneme in a word produces either nonsense, or a different word with a different meaning.

Restricted phonemes

A restricted phoneme is a phoneme that can only occur in a certain environment and has restrictions as to where it can occur.

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Restricted phonemes in English include:

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• {{IPA|/ŋ/}} as in sing can occur only at the end of a syllable or word and can never occur at the beginning of a word.
• Under most interpretations, {{IPA|/w/}} and {{IPA|/j/}} can occur only before a vowel and can never occur at the end of a syllable or word.
• {{IPA|/h/}} can occur only at the beginning of a syllable or word or at the beginning of a cluster and can never occur at the end of a syllable or word.
• Under most interpretations, in American accents with the cot-caught merger {{IPA|/ɔ/}} can occur only before /r/ and can never occur elsewhere.
• In non-rhotic accents, /r/ can only occur before a vowel or intervocalically and can never occur at the end of a word or before a consonant.