Nyāya Sūtras 5.8

5.8

yāvad arthaṃ vai nāmadheyaśabdās tair arthasampratyayaḥ, arthasampratyayāc ca vyavahāraḥ/ tatredam indriyārthasannikarṣād utpannam arthajñānaṃ ``rūpam'' iti vā, ``rasaḥ'' ity evaṃ vā bhavati, rūparasaśabdāś ca viṣayanāmadheyam/ tena vyapadiśyate jñānaṃ --- rūpam iti jānīte, rasa iti jānīte/ nāmadheyaśabdena vyapadiśyamānaṃ sat śābdaṃ prasajyate, ata āha --- avyapadeśyam iti/

As many objects as there are, so many indeed are the name-words; through them arises the comprehension of an object, and from the comprehension of an object arises practical behavior. In that regard, this cognition of an object produced from the contact of sense organ and object takes the form 'color' or 'taste'; and the words 'color' and 'taste' are names of the object. Cognition is designated by that: one cognizes [it] as 'color', one cognizes [it] as 'taste'. Being designated by a name-word, there would be the contingency of its being verbal; therefore he says: 'non-verbal'.