( ( ( Clouds , ) ( formed ( by ( condensed ( water vapor ) ) ) ) ) . )
(ROOT (NP (NP (NNS Clouds)) (, ,) (VP (VBN formed) (PP (IN by) (NP (JJ condensed) (NN water) (NN vapor)))) (. .)))
Clouds, formed by condensed water vapor.
(ROOT (S (NP (NNP Water) (NN vapor)) (VP (MD must) (VP (VB lose) (NP (NN heat) (NN energy)) (SBAR (IN before) (S (NP (NNS clouds)) (VP (MD can) (VP (VB form))))))) (. .)))
Water vapor must lose heat energy before clouds can form.