plate armour vs suit of armour

plate armour and suit of armour both are nouns.

Word	Noun	Adjective	Verb	Adverb
plate armour	Yes	No	No	No
suit of armour	Yes	No	No	No

As nouns, suit of armour is a hypernym of plate armour; that is, suit of armour is a word with a broader meaning than plate armour:

plate armour: a historical type of personal armor made from iron or steel plates, which superseded mail during the 14th century.
suit of armour: armor that protects the wearer's whole body

Other hypernyms of plate armour include body armor, body armour, cataphract, coat of mail, suit of armor.

plate armour (noun)	suit of armour (noun)
specially hardened steel plate used to protect fortifications or vehicles from enemy fire	armor that protects the wearer's whole body
a historical type of personal armor made from iron or steel plates, which superseded mail during the 14th century.