Vaisesika Sūtra 7.2.20

सामयिकः शब्दार्थप्रत्ययः ॥२०॥

sāmayikaḥ śabdārtha-pratyayaḥ ॥20॥

[सामयिकः (sāmayikaḥ) - conventional / relating to time; शब्द-अर्थ-प्रत्ययः (śabda-artha-pratyayaḥ) - cognition of word and meaning;]

The cognition of the word and its meaning is conventional (and is placed in the context of time).