retro-, anti-, an-

antacid (noun)

a substance that works against stomach acid

antibacterial (adjective)

designed to fight against or kill bacteria

antidote (noun)

a remedy or cure; something that works against a poison

antihistamine (noun)

a medicine that works against colds and allergies

antonym (noun)

a word that means the opposite of another word

retroactive (adjective)

goes back to a prior time

retrofit (verb)

to go back and install something that was not available at the time of original manufacturing

retrospective (adjective)

characterized by looking back at the past and reflecting; related to the past

retro, an, anti

backward, back against, opposite