As regards consonants, it will be useful to distinguish between the core system and a margin. The core system is made up of a number of proportion whose usual diagrammatic presentation offers a number of horizontal series, each a succession of phonemes produced at different points of the articulatory channel, but with a concomitant feature in common. What I call an order is precisely the class of phonemes articulated at the same point and with the same organs at that point; orders appears as vertical columns on the charts. For core consonants, we could devise the formulas of the very same type as the ones we have been suggesting for the vowels: a first digit would indicate the number of series; a second digit the number of orders. If we leave out the nasals and, for Greek, the fricatives, the consonantal core of classical Greek would be designated as ‘33’ (/p t k/, b d g/ /pʰ tʰ kʰ/), that of French as ‘26’ (/p f s t ʃ k /, /b v d z ʒ g/).
- Martinet (1962), Pag. 81