-ity

-ity is an English noun suffix used to nominalise adjectives to nouns, especially, to form the noun referring to the state, property, or quality of conforming to the adjective’s description.

This one is highly productive. Lots of examples

The main suffixations are:

• -al → -ality
• -able → -ability
• -ic → -icity
• -ive → -ivity
• -ous → -osity

Like many polysyllabic nouns, these tend to be stressed on the antepenultimate syllable. As -ity is two syllables, this will be the syllable before -ity. This occurs in cases where this syllable is part of another suffix (as in words in -ability (from -able) and -icity (from -ic)). Additionally, this shift typically results in a change in vowel quality; compare, for example, real and reality, where the sound [æ] in the second word is not present in the first. These vowel quality changes are usually consistent with the spelling of both forms — note that the letter <a> in the second word is present in the first — but sometimes spelling changes are seen, as with the suffix -ous, which when it combines with -ity produces the suffix -osity.

When a final -c is pronounced [k], before -ity it becomes [s]; compare, for example, elastic and elasticity.

Final -e is dropped before adding this suffix.

There are often French cognates, ending in the French spelling -ité.