What is "pro-"

Pro- \Pro-\ [L. pro, or Gr. ?. See Pro.] A prefix signifying before, in front, forth, for, in behalf of, in place of, according to; as, propose, to place before; proceed, to go before or forward; project, to throw forward; prologue, part spoken before (the main piece); propel, prognathous; provide, to look out for; pronoun, a word instead of a noun; proconsul, a person acting in place of a consul; proportion, arrangement according to parts.

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 "on behalf of, in place of, before, for, in exchange for, just as," which also was used as a prefix.\n

\nAlso 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- (cognates: 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, through" (see per).\n

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

Etymology 1 pre. 1 agreeing with; supporting; favouring 2 substituting for Etymology 2

pre. 1 earlier; prior 2 rudimentary 3 in front of