( Water ( ( can ( take ( ( the form ) ( of ( ( an ( invisible gas ) ) ( called ( water vapor ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Water)) (VP (MD can) (VP (VB take) (NP (NP (DT the) (NN form)) (PP (IN of) (NP (NP (DT an) (JJ invisible) (NN gas)) (VP (VBN called) (NP (NN water) (NN vapor)))))))) (. .)))
Water can take the form of an invisible gas called water vapor.
(ROOT (S (NP (NNP Water) (NN vapor)) (VP (VBZ exists) (PP (IN in) (NP (NP (DT the) (NN atmosphere)) (PP (IN as) (NP (DT an) (JJ invisible) (NN gas))))))))
Water vapor exists in the atmosphere as an invisible gas