helmet

nouns

armor plate that protects the head
helmet
is a part of
armor that protects the wearer's whole body
body armor, body armour, cataphract, coat of mail, suit of armor, suit of armour
is a type of (narrower)
specially hardened steel plate used to protect fortifications or vehicles from enemy fire
armor plate, armor plating, armour plate, plate armor, plate armour
a protective headgear made of hard material to resist blows
helmet
is a type of (narrower)
clothing for the head
headdress, headgear