Comments: Cf. also Kar. Tok. =iʕ-, Akhv. Tseg., Tl. =aʔ- 'know'. In Av. r- must be a historical prefix. In Av. and Akhv. a nominal derivate from this root means 'smth. heard; word, speech': Av. ráʕi (Chad. ráʕi), Akhv. req̇i.
An Ablaut variant of the same root may be PA *haq̇(Vn)- 'to see' (if the original meaning is reconstructed as 'to perceive').