KnowraPigeonhole principleLinked fromLinked fromThe 30 pages that link to Pigeonhole principle, each with the reason it gives.All 30Broader topic 1Related 23Narrower topic 2Compared with 4Birthday ProblemNarrower topic: It guarantees a match once a group exceeds the number of possible birthdays.Thue's lemmaNarrower topic: Elementary proofs of lattice-point existence often reduce to this broader counting idea.