A protective piece of armor designed to protect the cranium from damage. The design and shape can vary because of the time-period, setting, and what the helmet is to protect the cranium from.
If the helmet protects the entire head in a protective cover, it is a helm.
The following tags implicate this tag: american_football_helmet, baseball_helmet, bicycle_helmet, diving_helmet, hardhat, helm, helmet_removed, holding_helmet, horned_helmet, kabuto_(helmet), military_helmet, motorcycle_helmet, pickelhaube, pith_helmet, and winged_helmet (learn more).