cat|a|lyst

cat|a|lyst «KAT uh lihst», noun.

1. a substance that causes a chemical reaction while itself remaining practically unchanged: »

Catalysts are properly defined as substances that regulate the rate at which chemical reactions proceed. Some catalysts accelerate reactions…Other catalysts slow reactions. Examples of both types exist…within the cells and fluids of living organisms, where they are known as enzymes (Scientific American).

2. Figurative. a person or thing that brings about some change or changes, without being directly affected itself: »

The talent agent is the catalyst who brings performers and jobs together (Wall Street Journal). Job dissatisfaction and severe unemployment are catalysts to violence rather than primary causes (Morton Salkind).

Also, catalyzer.