catalyst

catalyst

n.
  1. a substance that initiates or accelerates a chemical reaction without itself being affected; as, thousands of enzymes serve in concert as calaysts to produce the sequence of reactions we call “life”; the industrial production of cheap ammonia depended on finding a good catalyst. (Chem.)
  2. something that serves as a precipitating occasion for an event; as, the invasion acted as a catalyst to unite the country.
  3. something or someone that causes events to happen with itself being changed.