( ( opaque ( ( A substance ) ( that ( ( does not ) ( allow ( light ( to ( pass ( through it ) ) ) ) ) ) ) ) ) . )
(ROOT (S (VP (VB opaque) (NP (NP (DT A) (NN substance)) (SBAR (WHNP (WDT that)) (S (VP (VBZ does) (RB not) (VP (VB allow) (ADJP (JJ light) (S (VP (TO to) (VP (VB pass) (PP (IN through) (NP (PRP it))))))))))))) (. .)))
opaque A substance that does not allow light to pass through it.
(ROOT (S (NP (NNP Opaque)) (VP (VBZ is) (NP (NP (DT the) (NN term)) (PP (IN for) (NP (NN matter))) (SBAR (WHNP (WDT that)) (S (VP (VBZ does) (RB not) (VP (VB let) (NP (DT any) (JJ light) (NN pass)) (PRT (RP through)))))))) (. .)))