Etymology
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ante- 
word-forming element meaning "before, in front of; previous, existing beforehand; introductory to," from Latin ante (prep., adv.) "before (in place or time), in front of, against," also used in compounds, from PIE *anti- "facing opposite, against," inflected form (locative singular) of root *ant- "front, forehead," with derivatives meaning "in front of, before."
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un- (2)
prefix of reversal, deprivation, or removal (as in unhand, undo, unbutton), Old English on-, un-, from Proto-Germanic *andi- (source also of Old Saxon ant-, Old Norse and-, Dutch ont-, Old High German ant-, German ent-, Gothic and- "against"), from PIE *anti "facing opposite, near, in front of, before, against" (from PIE root *ant- "front, forehead," with derivatives meaning "in front of, before").

More or less confused with un- (1) through similarity in the notions of "negation" and "reversal;" an adjective such as unlocked might represent "not locked" (un- (1)) or the past tense of unlock (un- (2)).
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praeter- 

from Latin adverb and preposition praeter "beyond, past, besides, except" (from PIE root *per- (1) "forward," hence "in front of, before"). See preter-, which now is the usual form of it in English; also see æ (1).

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presby- 

word-forming element meaning "old," from Greek presby-, combining form of presbys "elderly, aged," as a noun, "elder, old man," which is of uncertain and much debated origin and phonetic development (some Doric forms have -g- in place of -b-). The first element is likely *pres- "before, in front" (from PIE root *per- (1) "forward," hence "in front of, before, first"). Perhaps the whole originally meant "one who leads the cattle," from the root of bous "cow." Watkins, however, has it from PIE *pres-gwu- "going before," with second element from root *gw-u- "going," a suffixed form of root *gwa- "to come."

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ambi- 
word-forming element meaning "both, on both sides," from Latin ambi- "around, round about" (before vowels amb-, also sometimes reduced to am-, an-), from PIE root *ambhi- "around," which is probably an ablative plural (*ant-bhi "from both sides") of *ant- "front, forehead."
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preter- 

also praeter-, word-forming element meaning "beyond; over, more than in quantity or degree," from Latin praeter (adverb and preposition) "beyond, before, above, more than," properly comparative of prae "before," from PIE root *per- (1) "forward," hence "in front of, before."

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pro- 

word-forming element meaning "forward, forth, toward the front" (as in proclaim, proceed); "beforehand, in advance" (prohibit, provide); "taking care of" (procure); "in place of, on behalf of" (proconsul, pronoun); from Latin pro (adv., prep.) "on behalf of, in place of, before, for, in exchange for, just as," which also was used as a first element in compounds and had a collateral form por-.

Also in some cases from cognate Greek pro "before, in front of, sooner," which also was used in Greek as a prefix (as in problem). Both the Latin and Greek words are from PIE *pro- (source also of Sanskrit pra- "before, forward, forth;" Gothic faura "before," Old English fore "before, for, on account of," fram "forward, from;" Old Irish roar "enough"), extended form of root *per- (1) "forward," hence "in front of, before, toward, near," etc.

The common modern sense of "in favor of, favoring" (pro-independence, pro-fluoridation, pro-Soviet, etc.) was not in classical Latin and is attested in English from early 19c.

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ob- 

word-forming element meaning "toward; against; before; near; across; down," also used as an intensive, from Latin ob (prep.) "in the direction of, in front of, before; toward, to, at, upon, about; in the way of; with regard to, because of," from PIE root *epi, also *opi "near, against" (see epi-).

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anti- 

word-forming element of Greek origin meaning "against, opposed to, opposite of, instead," shortened to ant- before vowels and -h-, from Old French anti- and directly from Latin anti-, from Greek anti (prep.) "over, against, opposite; instead, in the place of; as good as; at the price of; for the sake of; compared with; in opposition to; in return; counter-," from PIE *anti "against," also "in front of, before" (from root *ant- "front, forehead," with derivatives meaning "in front of, before"), which became anti- in Italian (hence antipasto) and French.

It is cognate with Sanskrit anti "over, against," and Old English and- (the first element in answer). A common compounding element in Greek, in some combinations it became anth- for euphonic reasons. It appears in some words in Middle English but was not commonly used in English word formations until modern times. In a few English words (anticipate, antique) it represents Latin ante.

In noun compounds where it has the sense of "opposed to, opposite" (Antichrist, anti-communist) the accent remains on the anti-; in adjectives where it retains its old prepositional sense "against, opposed to," the accent remains on the other element (anti-Christian, anti-slavery).

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fore- 
Middle English for-, fore-, from Old English fore-, often for- or foran-, from fore (adv. & prep.), which was used as a prefix in Old English as in other Germanic languages with a sense of "before in time, rank, position," etc., or designating the front part or earliest time.
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