Is "Neither Rahul or Sameer came to the party" correct?

Why

Ayush's confusion is understandable, since "either" and "neither" look and sound so similar, and "either" genuinely does pair with "or" — "either Rahul or Sameer" is perfectly correct. But "either" and "neither" are opposite in meaning (one positive-ish choice, one total denial), and English keeps their partner words separate too, as a fixed, unshared pair: "either" always pairs with "or", while "neither" always pairs with "nor", never "or". Mixing them, as in "neither...or", breaks a pairing that native speakers learn as one fixed two-word unit, the same way "not only" always expects "but also" to complete it, never a different second half. Test: say the sentence with the correct pairing — "Neither Rahul nor Sameer came" — and notice it reads as one smooth, complete pattern, the way "either...or" does in its own correct form, while "neither...or" reads as a mismatched half-pair. His teacher is right: "neither" always pairs with "nor", not "or" — the two negative words belong together as their own fixed unit.