( ( In ( a ( reduction reaction ) ) ) ( ( -LRB- ( ( which ( always ( ( occurs simultaneously ) ( with ( an ( oxidation reaction ) ) ) ) ) ) -RRB- ) ) ( ( the ( reducing agent ) ) ( ( is ( ( the ( ( chemical or ) substance ) ) ( which ( ( -LRB- ( 1 -RRB- ) ) ( ( ( ( combines ( with oxygen ) ) or ) ( -LRB- ( 2 -RRB- ) ) ) ( ( loses electrons ) ( to ( the reaction ) ) ) ) ) ) ) ) . ) ) ) )
(ROOT (S (PP (IN In) (NP (DT a) (NN reduction) (NN reaction))) (PRN (-LRB- -LRB-) (SBAR (WHNP (WDT which)) (S (ADVP (RB always)) (VP (VBZ occurs) (ADVP (RB simultaneously)) (PP (IN with) (NP (DT an) (NN oxidation) (NN reaction)))))) (-RRB- -RRB-)) (NP (DT the) (JJ reducing) (NN agent)) (VP (VBZ is) (NP (NP (DT the) (NN chemical) (CC or) (NN substance)) (SBAR (WHNP (WDT which)) (S (PRN (-LRB- -LRB-) (NP (CD 1)) (-RRB- -RRB-)) (VP (VP (VBZ combines) (PP (IN with) (NP (NN oxygen)))) (CC or) (PRN (-LRB- -LRB-) (NP (CD 2)) (-RRB- -RRB-)) (VP (VBZ loses) (NP (NNS electrons)) (PP (TO to) (NP (DT the) (NN reaction))))))))) (. .)))
In a reduction reaction (which always occurs simultaneously with an oxidation reaction) the reducing agent is the chemical or substance which (1) combines with oxygen or (2) loses electrons to the reaction.
(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)))))))))) (. .)))