catalyst

A substance that speeds up a chemical reaction without being consumed; figuratively, a person or event that triggers significant change.

• catalyse/ˈkætəlaɪz/(v)催化
• catalytic/ˌkætəˈlɪtɪk/(adj)催化的

• catalyst for change
• act as a catalyst
• catalyst for growth
• powerful catalyst
• catalyst for reform

1. 1.The protest served as a catalyst for sweeping legislative reform. (figurative)
2. 2.Platinum acts as a catalyst in catalytic converters, helping convert toxic exhaust gases into less harmful substances. (chemistry)

• trigger/ˈtrɪɡər/— something that causes a reaction — more sudden
• stimulus/ˈstɪmjələs/— something that promotes activity
• impetus/ˈɪmpɪtəs/— a force that makes something happen

from Greek "katalysis" (dissolution) — "kata-" (down) + "lyein" (to loosen) — originally a chemistry term, adopted for figurative use