IPA: /ˈteɪstfəl.nəs/
KK: /ˈteɪstfəlnəs/
The quality of being pleasing and appropriate in style or design.
The tastefulness of the restaurant's decor made it a popular choice for special occasions.
Tastefulness → It is formed from "taste" (from Old French *taster*, meaning to perceive flavor) and "-ful" (meaning full of) and "-ness" (meaning the state of). The word "tastefulness" means the state of being full of taste or having good taste.
Think of 'taste' as the ability to perceive flavor, and when something is 'full of' that quality ('-ful') and in a certain 'state' ('-ness'), it becomes tastefulness.