( and ( SO3 ( ( is ( ( ( ( sulfur ( tri oxide ) ) , ) or ) ( sulfur trioxide ) ) ) . ) ) )
(ROOT (S (CC and) (NP (NNP SO3)) (VP (VBZ is) (NP (NP (NN sulfur) (NN tri) (NN oxide)) (, ,) (CC or) (NP (NN sulfur) (NN trioxide)))) (. .)))
and SO3 is sulfur tri oxide, or sulfur trioxide.
(ROOT (S (NP (NNP Sulfur)) (VP (MD can) (VP (VB combine) (PP (IN with) (NP (NN oxygen))) (S (VP (TO to) (VP (VB produce) (NP (NN sulfur) (NN trioxide))))))) (. .)))