Morphological contrast and merger: ranuki in Japanese

The central notion of structural linguistics is that of contrast or opposition: The linguistic value and role of a unit cannot be reduced to its physical substance, but is crucially determined by the network of relations that it enters into with other units of a similar kind: phoneme to phoneme, morpheme to morpheme, etc. A mid front vowel /e/ in a five-vowel system is something quite different from an /e/ in a seven-vowel system, perfect tense in a system without imperfect is something different from perfect tense in a system with imperfect, etc. Structuralist phonemics is the embodiment of a theory built on contrast as a central notion.