What I find interesting about the words “ante” and “anti” is that, in addition to acting as a prefix, each of them can stand alone. Although they may often sound the same and be confused one for the other, the two words do not have similar meanings, and they do not share the same root. According to the Webster’s New World Dictionary, “ante” is of Latin derivation and when used as a prefix means “before,” usually paired with other words denoting a particular time, event or physical space. For example: “antebellum” (adj. meaning “before the war” and used specifically to refer to the period of history before the American Civil War); “antediluvian” (adj. “before the flood,” used to refer to the period of history prior to the Biblical Flood or to something that is very old); “antechamber” (n. a smaller room leading into a larger or main room); and “antemortem” (adj. “before death”). As a standalone word, “ante” refers to the stake that each player must put into the pot before receiving cards, or to the act of putting that stake in.
“Anti,” on the other hand, is of Greek origin and when used as a prefix means “against,” as in “antiaircraft,” “antibacterial,” “antislavery,” and “antitoxin.” Standing alone, it refers to a person who is against a certain action, idea, etc., although personally I have never seen or heard the word anti used as a noun.
Keeping in mind the meanings of these two words may be of use to you when it comes time to remember how to spell any word that has the sounds “an – tee” in it. Unless you are referring to the honorific of a female relation who is a sibling of your mother or father, in which case you need to remember a third word which can act as a homophone of these two: “Auntie.”