accelerator [accelerators](substance which speeds up chemical reactions) noun [UK: ək.ˈse.lə.reɪ.tə(r)] [US: æk.ˈse.lə.ˌre.tər]
catalyst [catalysts](substance which increases the rate of a chemical reaction without being consumed in the process) noun [UK: ˈkæ.tə.lɪst] [US: ˈkæ.tə.ləst]