( Oxidation ( ( is ( ( a reaction ) ( ( in which ) ( oxygen ( combines ( with ( another substance ) ) ) ) ) ) ) . ) )
(ROOT (S (NP (NNP Oxidation)) (VP (VBZ is) (NP (NP (DT a) (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 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)))))))))) (. .)))