Webster's English Dictionary

catalysis

ca.tal.y.sis \k*-'tal-*-s*s\ \.kat-*l-'it-ik\ \-i-k(*-)le-\ n [Gk katalysis 
   dissolution, fr. katalyein to dissolve, fr. kata-)X cata- + lyein to 
   dissolve, release : modification and esp. increase in the rate of a 
   chemical reaction induce d by material unchanged chemically at the end of 
   the reaction; also : any reaction brought about by a separate agent - 
   cat.a.lyt.ic aj