WORD.

Catalyst

[kat-l-ist]

-noun
1. chemistry. a substance that cause or accelerates a chemical reaction without itself being affected.
2. something that causes activity between two or more persons or forces without itself being affected.
3. a person or thing that precipitates an event or change
4. a person whose talk, enthusiasm, or energy causes others to be more friendly, enthusiastic, or energetic.

Origin
1902, formed in Eng. (on analogyof analyst) from Gk. kata "down" + -lysis "a loosening" (comb. form)