ITy> A set or property of computational {search problem}s. A problem is NP-hard if solving IT in {polynomial time} would make IT possible to solve all problems in class NP in polynomial time. Some NP-hard problems are also in NP (these are called "NP-complete"), some are not. If you could reduce an NP problem to an NP-hard problem and then solve IT in polynomial time, you could solve all NP problems. See also computational complexITy. [Examples?] (1995-04-10)