From Teflpedia

-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.[1]

This one is highly productive. Lots of examples[2]

The main suffixations are:

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.

References[edit | edit source]