Rule for feminine · die
-keit → die · 0.8%
-keit is -heit's sister suffix: it also produces feminine abstract nouns (die), but usually attaches to adjectives ending in -lich, -sam, or -ig, as in die Möglichkeit (possibility, from "möglich"), die Öffentlichkeit (the public, from "öffentlich"), or die Aufmerksamkeit (attention, from "aufmerksam"). Just like -heit, it's a small but solid pattern - all 18 nouns in our list ending in -keit are feminine, with zero exceptions. Whenever you spot an adjective turned into a noun with -keit, you can safely go with die.