( ( catalyst ( reaction chamber ) ) ; )
(ROOT (NP (NP (NN catalyst) (NN reaction) (NN chamber)) (: ;)))
catalyst reaction chamber;
(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)) (. .)))