( ( ( A substance ) ( ( ( ( composed ( of ( chemical elements ) ) ) , ) or ) ( obtained ( by chemical ) ) ) ) ( processes . ) )
(ROOT (S (NP (NP (DT A) (NN substance)) (VP (VP (VBN composed) (PP (IN of) (NP (NN chemical) (NNS elements)))) (, ,) (CC or) (VP (VBN obtained) (PP (IN by) (NP (NN chemical)))))) (VP (VBZ processes)) (. .)))
A substance composed of chemical elements , or obtained by chemical processes.
(ROOT (S (S (NP (NN Element)) (VP (VBZ is) (NP (NP (DT the) (JJ basic) (NN chemical) (NN building) (NN block)) (PP (IN of) (NP (NN matter)))))) (: ;) (S (NP (PRP it)) (VP (VBZ is) (NP (DT the) (JJS simplest) (NN chemical) (NN substance)))) (. .)))