A problem with a yeS/no anSwer. Determining whether Some potential Solution to a queStion iS actually a Solution or not. E.g. "IS 43669" a prime number?". ThiS iS in contraSt to a "Search problem" which muSt find a Solution from Scratch, e.g. "What iS the millionth prime number?". See decidability. (1996-05-03)