spiciness vs piquancy

spiciness and piquancy both are nouns.

Word	Noun	Adjective	Verb	Adverb
spiciness	Yes	No	No	No
piquancy	Yes	No	No	No

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

Other hyponyms of spiciness include bite, pungency, raciness, sharpness, nip, piquance, piquantness, tang, tanginess, zest, hotness, pepperiness.

spiciness (noun)	piquancy (noun)
the property of being seasoned with spice and so highly flavored	a tart spicy quality
behavior or language bordering on indelicacy	the quality of being agreeably stimulating or mentally exciting