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definitions

-ity

a suffix used to form abstract nouns expressing state or condition: jollity; civility; Latinity.

Origin of -ity

variant of -itie, Middle English -ite < Old French < Latin -itāt- (stem of -itās); in many words representing Latin -itās directly
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for -ity

-ity

suffix forming nouns

indicating state or conditiontechnicality

Word Origin for -ity

from Old French -ite, from Latin -itās
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Word Origin and History for -ity

suffix forming abstract nouns from adjectives, meaning "condition or quality of being ______," from Middle English -ite, from Old French -ité and directly from Latin -itatem (nominative -itas), suffix denoting state or condition, composed of connective -i- + -tas (see -ty (2)).

Roughly, the word in -ity usually means the quality of being what the adjective describes, or concretely an instance of the quality, or collectively all the instances; & the word in -ism means the disposition, or collectively all those who feel it. [Fowler]
Online Etymology Dictionary, © 2010 Douglas Harper