# NP (complexity) #computer-science > NP is the set of decision problems for which the problem instances, where the answer is "yes", have proofs verifiable in polynomial time. There exists a verifier which can checks a solution is correct in polynomial time. > The complexity class co-NP for which the answer “no” can be verified in polynomial time. Verifier which checks the answer is wrong in polynomial time. 📖 [NP (complexity) - Wikipedia](https://en.wikipedia.org/wiki/NP_(complexity))