Stimulant, motivation and incentive are words. Those mean catalyst.
For example the ammonia production; the magnetite catalyst is the most common.
THE NAME OF THE CATALYST WHICH HASTENS THE RATE OF REACTION OF FOOD BUT DOES NOT PART IN THE DIGESTION IS KNOWN AS A CATALYST KNOWN AS MAGANESE(IV)OXIDE.
Platinum, palladium and rhodium are metals used as catalyst in converters.
one name for a catalyst is... to be onis i have no idea myself xxx
biological catalysts
bait, catalyst, encouragement, consideration.
inhibitor
Catalyst
I'm not sure that its a synonym, but it is a biological catalyst
Enzymes
The enzyme that activates another enzyme is called a kinase. Kinases add phosphate groups to proteins, a process known as phosphorylation, which can activate or deactivate the target enzyme.
A catalyst is a character tha brings about change in the story. For example, a catalyst's actions could cause one character to lose trust in another, or something of the sorts. Basically, if the story takes a different course because of a certain character, that character would be a catalyst.