( ( Hydrogen oxide ) ( ( ( ( is ( water ( in ( vapor form ) ) ) ) and ) ( just ( adds ( to ( ( the ( water portion ) ) ( of air ) ) ) ) ) ) . ) )
(ROOT (S (NP (NN Hydrogen) (NN oxide)) (VP (VP (VBZ is) (NP (NP (NN water)) (PP (IN in) (NP (NN vapor) (NN form))))) (CC and) (VP (ADVP (RB just)) (VBZ adds) (PP (TO to) (NP (NP (DT the) (NN water) (NN portion)) (PP (IN of) (NP (NN air))))))) (. .)))
Hydrogen oxide is water in vapor form and just adds to the water portion of air.
(ROOT (S (NP (NNP Water)) (VP (VBZ is) (NP (NP (DT an) (NN oxide)) (PP (IN of) (NP (NN hydrogen))))) (. .)))