tact vs tactfulness

tact and tactfulness both are nouns.

Word	Noun	Adjective	Verb	Adverb
tact	Yes	No	No	No
tactfulness	Yes	No	No	No

As nouns, tact and tactfulness are synonyms defined as:

tact and tactfulness: consideration in dealing with others and avoiding giving offense

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

tact: consideration in dealing with others and avoiding giving offense
tactfulness: Behavior or actions characterized by careful consideration in dealing with others, to avoid giving offense.

Other hyponyms of tact include delicacy, diplomacy, discreetness, finesse, address, savoir-faire.

tact (noun)	tactfulness (noun)
consideration in dealing with others and avoiding giving offense	consideration in dealing with others and avoiding giving offense
	Behavior or actions characterized by careful consideration in dealing with others, to avoid giving offense.