( ( for ( ( water vapor ) ( to form ) ) ) ( , ( they ( ( must ( move ( far apart ) ) ) . ) ) ) )
(ROOT (S (PP (IN for) (NP (NP (NN water) (NN vapor)) (PP (TO to) (NP (NN form))))) (, ,) (NP (PRP they)) (VP (MD must) (VP (VB move) (ADVP (RB far) (RB apart)))) (. .)))
for water vapor to form, they must move far apart.
(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.