The relational gaps between the sounds of a language are just as necessary to the psychological definition of these sounds as the articulations and acoustic images which are customarily used to define them.
- Sapir (1925), a pag.35

Each member of this system is [...] characterized by a distinctive and slightly variable articulation and a corresponding acoustic image [...]
- Sapir (1925), a pag.35

[...] a speech sound is not merely an articulation or an acoustic image, but material for symbolic expression in an appropriate linguistic context.
- Sapir (1925), a pag.44