ace vs singleton

ace and singleton both are nouns.

Word	Noun	Adjective	Verb	Adverb
ace	Yes	Yes	Yes	No
singleton	Yes	No	No	No

As nouns, singleton is a hyponym of ace; that is, singleton is a word with a more specific, narrower meaning than ace:

Other hyponyms of ace include monad, monas.

ace (noun)	singleton (noun)
a serve that the receiver is unable to reach	the playing card that is the only card in a suit held in a bridge hand as initially dealt
one of four playing cards in a deck having a single pip on its face	a set containing a single member
someone who is dazzlingly skilled in any field	a single object (as distinguished from a pair)
the smallest whole number or a numeral representing this number

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