plate armor vs cataphract

plate armor and cataphract both are nouns.

Word	Noun	Adjective	Verb	Adverb
plate armor	Yes	No	No	No
cataphract	Yes	No	No	No

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

plate armor: a historical type of personal armor made from iron or steel plates, which superseded mail during the 14th century.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

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

plate armor (noun)	cataphract (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a historical type of personal armor made from iron or steel plates, which superseded mail during the 14th century.