( Oxidation ( ( is ( ( a ( chemical reaction ) ) ( ( in which ) ( oxygen ( combines ( with ( another substance ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Oxidation)) (VP (VBZ is) (NP (NP (DT a) (JJ chemical) (NN reaction)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (NN oxygen)) (VP (VBZ combines) (PP (IN with) (NP (DT another) (NN substance)))))))) (. .)))
Oxidation is a chemical reaction in which oxygen combines with another substance.
(ROOT (S (NP (DT A) (NN combination) (NN reaction)) (VP (VBZ is) (NP (NP (DT a) (NN reaction)) (SBAR (WHPP (IN in) (WHNP (WDT which))) (S (NP (CD two) (CC or) (JJR more) (NNS substances)) (VP (VBP combine) (S (VP (TO to) (VP (VB form) (NP (DT a) (JJ single) (JJ new) (NN substance)))))))))) (. .)))