What is a prefix meaning against, opposite or opposed to, contrary, or in place of; -- used in composition in many English words. It is often shortened to ant-; as, antacid, antarctic called?

anti — A prefix meaning against, opposite or opposed to, contrary, or in place of; -- used in composition in many English words. It is often shortened to ant-; as, antacid, antarctic. (Webster's 1913.)

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