The Suffix "-ość"
To turn an adjective into an abstract noun in Polish, you simply drop the adjective's final vowel (usually -y or -i) and add the suffix -ość. This works just like the English suffixes "-ness", "-ity", or "-ty".
Every noun ending in -ość is feminine. Let's look at the word for "curiosity", derived from the adjective ciekawy (curious).
Personal Traits and States of Mind
This suffix is incredibly useful for discussing personal traits and states of mind. For example, szczery (honest) becomes szczerość (honesty), and uprzejmy (polite) becomes uprzejmość (politeness).
Similarly, mądry (wise) gives us mądrość (wisdom), and naiwny (naive) gives us naiwność (naivety).
From Adjective to Noun
Let's compare an adjective describing someone with the abstract noun itself. Notice how the adjective matches the gender of the noun it modifies, while the abstract noun in -ość is a fixed feminine concept.
First, using lojalny (loyal) and lojalność (loyalty):
Next, using wrażliwy (sensitive) and wrażliwość (sensitivity). Notice how the adjective becomes wrażliwa to describe a female subject:
Because these are nouns, they decline (change endings) depending on their role in the sentence.
Often, you will talk about having "a lot of" a trait, or "lacking" a trait. Words indicating quantity like dużo (a lot), or the verb brakuje (is missing / lacks), require the noun that follows to be in the Genitive case. For feminine nouns ending in -ość, the Genitive ending is -ości.