Terminology


A phoneme is a category or mental representation of a sound which may include a set of differing "surface" variants or allophones, all of which are considered by native speakers to be the same sound.

An allophone is a predictable (=contextual) variant of a phoneme.

Example: [p^h] and [p] are allophones of the phoneme /p/.

A minimal pair is a pair of words which differ on only one sound in the same position.  Every minimal pair will allow you to conclude that the differing sounds are phonemic (=contrastive=distinctive).

Example: [beId] 'bade'  & [peId] 'paid' ; conclusion: /b/ and /p/ are different phonemes.

To say that 2 sounds contrast in a language (or are contrastive) means that they are different phonemes.

An overlapping distribution between sounds is defined by shared contexts (or environments) in which the sounds occur. If sounds are in overlapping distribution, this is likely to be proof that they are contrastive, i.e. allophones of different phonemes. The one exception is free variation (see below).
Another way to describe overlapping distribution in which the sounds occur in the same environment and result in a change in word meaning is contrastive distribution.

Complementary distribution between sounds means that one sound occurs in an environment where the other does not. If two sounds are in complementary distribution, this means that their appearance is predictable by phonetic context. Examples of contexts are: word-initial position, between two vowels, before a voiced sound, after a voiceless stop, word-final position, etc). To be predictable means that you can say with certainty, given any environment, which sound will appear and which one will not.

Free variation occurs when two sounds can occur in the same context (=environment) without the meaning of a word changing. Example: released t and unreleased t. These can both occur in word-final position. Therefore, their environments are overlapping, but since no difference in meaning results from the change from one to the other, these sounds must be considered allophones of the same phoneme.