( ( ( A ( negative catalyst ) ) ( -LRB- ( ( ( inhibitor , ) retarder ) -RRB- ) ) ) ( ( ( slows down ) ( a ( chemical reaction ) ) ) . ) )
(ROOT (S (NP (NP (DT A) (JJ negative) (NN catalyst)) (PRN (-LRB- -LRB-) (NP (NP (NN inhibitor)) (, ,) (NP (NN retarder))) (-RRB- -RRB-))) (VP (VBZ slows) (PRT (RP down)) (NP (DT a) (JJ chemical) (NN reaction))) (. .)))
A negative catalyst (inhibitor, retarder) slows down a chemical reaction.
(ROOT (S (SBAR (IN If) (S (NP (DT a) (NN catalyst)) (VP (VBZ runs) (PRT (RP out))))) (, ,) (NP (DT the) (NN reaction)) (VP (VBZ slows)) (. .)))