EntityQ2891260· pop 20· linked from 381 articleswicked problemSign in to saveproblem that is difficult or impossible to solve because of incomplete, contradictory, and changing requirements that are often difficult to recognizeConnectionsclimate changeEntitysystems theoryEntitysocial issueEntitymathematicsEntitypoliticsEntitychessEntitylawEntitytechnologyEntitysocietyEntityHIV/AIDSEntityInternational Standard Book NumberEntitynuclear weaponEntityideologyEntityeconomyEntitynatural environmentEntitynatural disasterEntitysexually transmitted infectionEntityWayback MachineEntityStanford UniversityEntitydigital object identifierEntityCategories1967 introductionsCognitionPolicyProblem solving