guarantee [guarantees](anything that assures a certain outcome) noun [UK: ˌɡæ.rən.ˈtiː] [US: ˌɡe.rən.ˈtiː]
warranty [warranties](legal: an agreement which states that the goods or property in question will be in exactly the same state as promised) noun [UK: ˈwɒ.rən.ti] [US: ˈwɔː.rən.ti]