ace of spades vs ace

ace of spades and ace both are nouns.

Word	Noun	Adjective	Verb	Adverb
ace of spades	Yes	No	No	No
ace	Yes	Yes	Yes	No

As nouns, ace is a hypernym of ace of spades; that is, ace is a word with a broader meaning than ace of spades:

ace of spades: the ace in the spade suit; sometimes taken as a portent of death
ace: one of four playing cards in a deck having a single pip on its face

ace of spades (noun)	ace (noun)
the ace in the spade suit; sometimes taken as a portent of death	a serve that the receiver is unable to reach
	one of four playing cards in a deck having a single pip on its face
	someone who is dazzlingly skilled in any field
	the smallest whole number or a numeral representing this number

ace of spades (adjective)	ace (adjective)
	of the highest quality