before a vowel, brachi-, word-forming element meaning "arm, of the upper arm, pertaining to the upper arm and," from Latinized form of Greek brakhion "arm," perhaps originally "upper arm," literally "shorter," from brakhys "short" (from PIE root *mregh-u- "short"), in contrast to the longer forearm.
before vowels pleur-, word-forming element meaning "pertaining to the side; pertaining to the pleura," from Greek pleura "the side, the ribs" (see pleura).
word-forming element meaning "on the near side of, on this side," from Latin preposition cis "on this side" (in reference to place or time), related to citra (adv.) "on this side," from PIE *ki-s, suffixed form of root *ko-, the stem of demonstrative pronoun meaning "this." Opposed to trans- or ultra-. Originally only of place, sometimes 19c. of time; 21c. of life situations (such as cis-gender, which is attested by 2011).
word-forming element meaning "beyond" (ultraviolet) or "extremely" (ultramodern), from Latin ultra- from ultra (adv. and prep.) "beyond, on the other side, on the farther side, past, over, across," from PIE *ol-tero-, suffixed form of root *al- "beyond." In common use from early 19c., it appears to have arisen from French political designations. As its own word, a noun meaning "extremist" of various stripes, it is first recorded 1817, from French ultra, shortening of ultra-royaliste "extreme royalist."
before vowels plagi-, word-forming element meaning "slanting, oblique," from Greek plagios "oblique, slanting," from plagos "side," from PIE *plag- "flat, spread," variant form of root *plak- (1) "to be flat."
word-forming element meaning "above, over, beyond, before," from Latin supra "above, over, before, beyond, on the upper side," in supera (parte), literally "on the upper (side)," from old fem. ablative singular of superus (adj.) "above," related to super "above, over" (from PIE root *uper "over"). In English interchangeable with, but somewhat more technical than, super-. Rare as a prefix in Latin, more common in Medieval Latin, in English chiefly scientific or technical.
word-forming element meaning "oblique," before vowels lox-, from Greek loxos "bent to the side, slanting, oblique," figuratively "ambiguous," a word of uncertain origin. As in loxodromics "art of oblique sailing" (1670s).
before vowels, cephal-, word-forming element meaning "head, skull, brain," Modern Latin combining form of Greek kephalē "head, uppermost or top part, source," from PIE *ghebh-el- (source also of Tocharian spal "head;" Old High German gebal "skull;" also, via the notion of "front," Gothic gibla, Old Norse gafl "side of a facade").
word-forming element meaning "across, beyond, through, on the other side of, to go beyond," from Latin trans (prep.) "across, over, beyond," perhaps originally present participle of a verb *trare-, meaning "to cross," from PIE *tra-, variant of root *tere- (2) "cross over, pass through, overcome." In chemical use indicating "a compound in which two characteristic groups are situated on opposite sides of an axis of a molecule" [Flood].
word-forming element meaning "below, beneath," from Latin infra (adverb and preposition) "below, underneath, on the under side, beneath," also "later than; smaller than; inferior to," related to infernus "low, below," from PIE *ndher "under" (source also of Sanskrit adnah "below," Old English under "under, among;" see under). Modern popular use of it dates from the 1920s, as an opposite to super-, often in science fiction. "This use of infra- is scarcely a Latin one" [OED].
