Contrastive distribution

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Contrastive distribution is when two elements can appear in the same environment, but swapping one for the other changes the meaning. It is often shown with a minimal pair.

It is different from:
- Complementary distribution: two elements never occur in the same environment and cannot be swapped.
- Free variation: two elements can occur in the same environment and swap without changing meaning.

In phonology, two sounds are in contrastive distribution if replacing one with the other in the same environment changes meaning. This shows they belong to different phonemes. Example: in English, the sounds [pʰ] and [b̥] can start a word (pat vs bat). They occur in the same position but change the word’s meaning, so they are in contrastive distribution.

In morphology, two morphemes are in contrastive distribution if they appear in the same position but have different meanings. For example, in Korean, nominative case markers are /-ka/, /-i/, and /-(l)ul/. If a noun ends in a consonant, /-i/ is used; otherwise /-ka/. The accusative marker /-(l)ul/ can also occupy the same slot and has a different function. Therefore, /-(l)ul/ and the set {/-i/, /-ka/} are in contrastive distribution.

In syntax, mood forms can be contrastive. In English, the indicative and the subjunctive mood contrast: changing from the non-past first-person singular indicative am to the subjunctive were changes the grammatical mood of the sentence.