(Indo-European linguistics) In Proto-Indo-Europeanlinguistics, an ablaut form of a Proto-Indo-European root, characterised by the presence of the */o/ vowel phoneme in place of */e/.
Ancient Greek γόνος(gónos) is a reflex of *ǵónh₁os(“race”), which is itself an o-grade derivative of the root *ǵenh₁-(“to beget; to produce, bear”).