is this a feminine noun?
I think the nouns ending in a soft consonant (like ć, dź) are quite often feminine, maybe even predominantly.
Almost all the nouns ending in -ość (often made from an adjective):
stary - starość,
wielki - wielkość,
długi - długość,
radość (joy) (from old adjective "rad" today rarely used)
are feminine, and it's a big group of words.
With those nouns ending in -ość, but not derived from an adjective, it's not always the rule, for example:
ość (fish bone),
kość (bone),but masculine: gość (guest)
Other nouns with -ść at the end (besides -ość) are usually feminine too:
wieść - news (today rather in the modern form of wiadomość),
część - part,
cześć - honour,
treść - content (mainly figuratively - of a book, a text, content of a container, recipient = zawartość)
but there are masculine too, for example referring to male persons, like teść (father-in-law).
chęć - will,
rtęć - mercury (metal - quicksilver, not the planet or the Greek god which are called Merkury)
but zięć (son-in-law) is of course masculine
-dź (spowiedź - confession)
-ń is probably usually masculine (although I'm not sure)
sień (part of a house, dunno the English word)
grań (in mountains, dunno the English word)
but dzień (day) is masculine (I think dzień - noc simply followed the Latin pattern with the gender: masculin for day and feminine for night, which must have had some religious meaning), also masculine is waleń (a species of whale), kleń (some fish, don't know what it's called in English)
- ż (młodzież - youth, odzież - clothes), I guess -rz ending is typically masculine
(Here I stop this post, because there are simply too many examples, sorry).