I have noticed that in many languages, words for "no", negative verb forms, etc. often begin with the sound /n/. Although I understand it is by no means universal, is there any relationship between these sounds in otherwise unrelated languages (e.g. English "no", Japanese "-nai", and many more), or is it purely coincidental?
From Online Etymology Dictionary's entry of "un"-
prefix of negation, O.E. un-, from P.Gmc. *un- (cf. O.Fris., O.H.G., Ger. un-, Goth. un-, Du. on-), from PIE *n- (cf. Skt. a-, an- "not," Gk. a-, an-, O.Ir. an-, L. in-), a variant of PIE base *ne- "not" (cf. Avestan na, O.C.S., Lith. ne "not," L. ne "that not," Gk. ne- "not," O.Ir. ni, Corn. ny "not").
So the theory is that the root (possibly *ne-) traces back to the Proto-Indo-European language, the theoretical ancestor of the Indo-European languages (including English, Latin, and the majority of European and Indian languages, with total of 3 billion native speakers), which is why you can observe that it's very common.
That said, Japanese doesn't belong to this group, so possibly it's just a coincidence. Seing from this list of translations of "no" in many languages, I don't observe it being common outside of Indo-European languages.Tweet