# The Satisfiability problem is in NP
Last edited: 2026-01-28
# Statement
Lemma
The Satisfiability problem is in NP .
# Proof
First note that it is in the form of a search problem as it either provides you with a satisfying assignment to the $n$ variables or says one doesn’t exist.
All that is left to show is that we can verify an answer in Polynomial time .
Given an assignment of values to the $n$-variables, checking whether one clause is satisfied takes $O(n)$ time. There are $m$ clauses, so in total this takes $O(nm)$ time.
This is polynomial so the Satisfiability problem is in NP .