plate armour vs aegis

plate armour and aegis both are nouns.

Word	Noun	Adjective	Verb	Adverb
plate armour	Yes	No	No	No
aegis	Yes	No	No	No

As nouns, aegis is a hyponym of plate armour; that is, aegis is a word with a more specific, narrower meaning than plate armour:

plate armour: specially hardened steel plate used to protect fortifications or vehicles from enemy fire
aegis: armor plate that protects the chest; the front part of a cuirass

plate armour (noun)	aegis (noun)
specially hardened steel plate used to protect fortifications or vehicles from enemy fire	kindly endorsement and guidance
a historical type of personal armor made from iron or steel plates, which superseded mail during the 14th century.	armor plate that protects the chest; the front part of a cuirass