Pro- is another prefix that exists in two forms. The first comes from Latin pro, meaning ?for.? In English, this pro- usually means ?favoring? or ?supporting,? as when it is prefixed to names of nationalities: pro-American. In this sense, the opposite of pro- would be anti: proslavery/antislavery.    1
  The other pro- comes from Greek pro, meaning ?before, in front.? The word prologue comes from Greek prologos, from pro- plus logos, meaning ?speech.? In English, pro- often means ?before? or ?earlier? and is used mainly in science terms: prophase.    2