1. 催化剂;诱因;诱导者
You can describe a person or thing that causes a change or event to happen as a catalyst .

2. (化学)催化剂
In chemistry, a catalyst is a substance that causes a chemical reaction to take place more quickly.

1. something that causes an important event to happen

e.g. the invasion acted as a catalyst to unite the country

2. (chemistry) a substance that initiates or accelerates a chemical reaction without itself being affected

Synonym: accelerator