( Condensation ( : ( ( ( The ( water vapor ) ) ( then ( cools ( to ( form ( ( clouds or ) fog ) ) ) ) ) ) . ) ) )
(ROOT (FRAG (NP (NNP Condensation)) (: :) (S (NP (DT The) (NN water) (NN vapor)) (ADVP (RB then)) (VP (VBZ cools) (S (VP (TO to) (VP (VB form) (NP (NNS clouds) (CC or) (NN fog))))))) (. .)))
Condensation: The water vapor then cools to form clouds or fog.
(ROOT (S (NP (NNP Condensation)) (VP (MD must) (VP (VB occur) (PP (IN for) (NP (NNS clouds))) (S (VP (TO to) (VP (VB form)))))) (. .)))