a suffix used to form abstract nouns from adjectives with stems in -t, -te, -tic, and especially -nt (democracy; accuracy; expediency; stagnancy; lunacy), and sometimes used to form action nouns (vacancy; occupancy).
2.
a suffix of nouns denoting rank or office, sometimes attached to the stem of a word rather than to the word itself:
captaincy; magistracy.
Origin
representing French-cie, -tie,Latin-cia, -tia,Greek-kia, -keia, -tia, -teia; in most cases to be analyzed as consonant + -y3: the consonant making the whole or the last member of the preceding morpheme
British Dictionary definitions for -cy
-cy
suffix
1.
(forming nouns from adjectives ending in -t, -tic, -te, and -nt) indicating state, quality, or condition: plutocracy, lunacy, intimacy, infancy
2.
(forming abstract nouns from other nouns) rank or office: captaincy
Word Origin
via Old French from Latin -cia, -tia, Greek -kia, -tia, abstract noun suffixes
Word Origin and History for -cy
abstract noun suffix of quality or rank, from Latin -cia, -tia, from Greek -kia, -tia, from abstract ending -ia + stem ending -c- or -t-. The native correspondents are -ship, -hood.