trans- Look up trans- at Dictionary.com
word-forming element meaning "across, beyond, through, on the other side of, to go beyond," from Latin trans-, from trans (prep.) "across, over, beyond," perhaps originally present participle of a verb *trare-, meaning "to cross," from PIE *tra-, variant of root *tere- (2) "to cross over" (see through). In chemical use indicating "a compound in which two characteristic groups are situated on opposite sides of an axis of a molecule" [Flood].