for

For is a small word that earns most of its living as a prefix. Bolt it onto a verb and you get the action plus "away": foriri, forlasi, forkuri, forpreni, forĵeti, forpeli. Four of those are common enough to have their own entries in the top thousand. Standing alone it is an adverb of place, so esti for is to be away or gone, and for de gives you the point departed from. As a bare exclamation, For! is a shout of get out, and For la milito! is how a placard says down with war.