The addition of -ity to an adjective results in a shift of stress to the antepenultimate syllable; that is, words in -ity are stressed on the last syllable before the -ity, even in cases where this syllable is part of another suffix (as in words in -ability and -icity).
adjective, dumber, dumbest. 1. lacking intelligence or good judgment; stupid; dull-witted. 2. lacking the power of speech (offensive when applied to humans): a dumb animal.
Key Difference: Stupid, Dumb and Idiot are all used as slang to refer to someone or something that lacks intelligence or common sense. The terms stupid, dumb, and idiot are words that are often used synonymously. The confusion among many rises from the fact that definitions of these words are quite similar.