from Latin prō (adv and prep). In compound words borrowed from Latin, prō- indicates: forward, out (project); forward and down (prostrate); away from a place (prodigal); onward in time or space (proceed); extension outwards (propagate); before in time or place (provide, protect); on behalf of (procure); acting as a substitute for (pronominal); and sometimes intensive force (promiscuous)
before in time or position; anterior; forward prophase, procephalic, prognathous
from Greek pro (prep) before (in time, position, rank, etc)
prefix meaning "before, forward, in favor of, in place of," from L. pro "on behalf of, in place of, before, for," also in some cases from cognate Gk. pro "before, in front of," both from PIE *pro-, extended form of base *por- "forward, through" (cf. Skt. para "beyond," pra- "before, forward, forth;" Gk. paros "before," para- "from beside, against, beyond;" Goth. faura "before," O.E. fore "before, for, on account of," fram "forward, from"). Pro and con is attested from c.1400, short for pro and contra "for and against" (L. pro et contra).