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definitions

-acy

a suffix of nouns of quality, state, office, etc., many of which accompany adjectives in -acious or nouns or adjectives in -ate: fallacy; papacy; legacy; delicacy; piracy.

Origin of -acy

< Latin -ācia, -ātia (spelling interchangeably in Medieval Latin, reflecting the Rom merger of the forms); these are in turn complexes of -āc- and -āt- -ate1 + -ia -y3. Cf. -cracy
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019