( Sound ( ( is ( ( a wave ) ( that ( travels ( through ( ( ( a medium ) , ) ( such ( as air ) ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Sound)) (VP (VBZ is) (NP (NP (DT a) (NN wave)) (SBAR (WHNP (WDT that)) (S (VP (VBZ travels) (PP (IN through) (NP (NP (DT a) (NN medium)) (, ,) (PP (JJ such) (IN as) (NP (NN air)))))))))) (. .)))
Sound is a wave that travels through a medium, such as air.
(ROOT (S (NP (NNP Medium)) (VP (VBZ is) (NP (NP (DT the) (NN matter)) (SBAR (WHPP (IN through) (WHNP (WDT which) (NN sound))) (S (NP (NNS waves)) (VP (VBP travel)))))) (. .)))