thoughtfulness vs tact

thoughtfulness and tact both are nouns.

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

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

Other hyponyms of thoughtfulness include attentiveness, tactfulness.

thoughtfulness (noun)	tact (noun)
a considerate and thoughtful act	consideration in dealing with others and avoiding giving offense
the trait of thinking carefully before acting
kind and considerate regard for others
a calm, lengthy, intent consideration