( ( a ( pure substance ) ) ( ( composed ( of ( ( ( ( two or ) more ) elements ) ( ( whose composition ) ( is constant ) ) ) ) ) . ) )
(ROOT (S (NP (DT a) (JJ pure) (NN substance)) (VP (VBN composed) (PP (IN of) (NP (NP (QP (CD two) (CC or) (JJR more)) (NNS elements)) (SBAR (WHNP (WP$ whose) (NNS composition)) (S (VP (VBZ is) (ADJP (JJ constant)))))))) (. .)))
a pure substance composed of two or more elements whose composition is constant.
(ROOT (S (ADVP (DT All) (NN matter) (SBAR (IN in) (S (NP (DT the) (NN universe)) (VP (VBZ is) (UCP (VP (VBN composed) (PP (IN of) (NP (CD one)))) (CC or) (ADJP (RBR more) (JJ unique))))))) (NP (JJ pure) (NNS substances)) (VP (VBD called) (NP (NNS elements))) (. .)))