( Clouds ( ( are ( formed ( by ( ( the condensation ) ( of ( atmospheric ( water vapor ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNS Clouds)) (VP (VBP are) (VP (VBN formed) (PP (IN by) (NP (NP (DT the) (NN condensation)) (PP (IN of) (NP (JJ atmospheric) (NN water) (NN vapor))))))) (. .)))
Clouds are formed by the condensation of atmospheric water vapor.
(ROOT (S (NP (NNP Condensation)) (VP (MD must) (VP (VB occur) (PP (IN for) (NP (NNS clouds))) (S (VP (TO to) (VP (VB form)))))) (. .)))