Vergeblich, vergebens, umsonst* = in vain, for nothing   Ich habe dreimal vergeblich (vergebens) versucht, ihn anzurufen.   I've tried to call him three times (and did not reach him).   Er ist umsonst gekommen.   He came for nothing.

* Between umsonst and vergeblich is a very fine difference. Vergeblich means, that the action itself could not be done. Umsonst means, that it could be done, only the result is not what was hoped for.

compare these phrases   a) Er hat das Buch umsonst gesucht.   He searched the book for nothing.   b) Er hat das Buch vergeblich gesucht.   He searched the book in vain.