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: horned_helmet, winged_helmet, motorcycle_helmet, pith_helmet, diving_helmet, bicycle_helmet, helm, hardhat, kabuto, baseball_helmet, football_helmet, helmet_removed, stahlhelm, holding_helmet, brodie_helmet, and pickelhaube (learn more).