cardinal vs four

cardinal and four both are nouns.

Word	Noun	Adjective	Verb	Adverb
cardinal	Yes	Yes	No	No
four	Yes	Yes	No	No

cardinal (noun)	four (noun)
crested thick-billed North American finch having bright red plumage in the male	a playing card or domino or die whose upward face shows four pips
a variable color averaging a vivid red	the cardinal number that is the sum of three and one
(Roman Catholic Church) one of a group of more than 100 prominent bishops in the Sacred College who advise the Pope and elect new Popes
the number of elements in a mathematical set; denotes a quantity but not the order

cardinal (adjective)	four (adjective)
being or denoting a numerical quantity but not order	being one more than three
serving as an essential component