Today I was trying to reconstruct some PIE roots by myself and I came across the word for '(to) know' in different indo-european languages. Here are some examples:
- Eng. (to) know
- It. conoscere
- Lat. (g)nōscō (I know); nōtus (known)
- Gr. γιγνώσκω gignōskō
- Skr. जानाति jānāti (he knows); ज्ञात jñātá (known); ज्ञातृ jñātṛ (someone who knows)
In Sanskrit PIE vowels *a (< *h₂e), *e and *o all merged into अ a, nevertheless we could guess the original vowel quality looking at Greek. Since it has an ω ō I thought that PIE could show an alternation of the kind *ǵneh₃- ~ *ǵn̥h₃- and wikipedia seems to confirm my guess (cfr. the root ǵneh₃-).
If we read the reconstruction that wikipedia proposes, we can see that the Sanskrit forms are augmented with a nasal infix (in fact the verbal base belongs to the ninth class) resulting in *ǵn̥-né-h₃-ti ~ *ǵn̥-n-h₃-énti. Now the root has the zero grade. I know that the resonant *n̥ evolves regularly in अ a in Sanskrit, but why is it long in the verb जानाति jānāti? The long a also appears in the past participle and in the nomen agentis formed upon the same root. Why is that?
Finally Latin and Greek forms seem also quite strange to me. According to wikipedia's article, they are based on *ǵn̥h₃-sḱé-ti which is a kind of present with the durative-iterative suffix -sḱé. In Greek this verb shows a reduplication too. My doubt is one more time about the quantity of the radical vowel. Why is it long both in Latin and Greek? If the suffix *-sḱé requires the zero grade, the laryngeal could develop a short *e that is subsequently colored to *o when the laryngeal is lost, but then this vowel should remain short. Only in the e-grade the laryngeal could color the preceding vowel and then lengthen it when lost.
Is there some phonetic law that explains why these forms have a long vowel? Or it's just a case of analogy?