The phonemes of a language are [...] distinct systems peculiar to the given language, and its words must be made up, in unconsious theory if not always in actualized behavior, of these phonemes. Languages differ very widely in their phonemic structures. But whatever the details of these structures may be, the important fact remains that there is no known language which has not a perfectly definite phonemic system.
- Sapir (1933a), a pag.8