CATA

Cat"a. Etym: [Gr. kata`.]

Definition: The Latin and English form of a Greek preposition, used as a prefix to signify down, downward, under, against, contrary or opposed to, wholly, completely; as in cataclysm, catarrh. It sometimes drops the final vowel, as in catoptric; and is sometimes changed to cath, as in cathartic, catholic.

Source: Webster’s Unabridged Dictionary 1913 Edition