1.
catalyst
A substance that speeds up a chemical reaction without being consumed in the process.
Forms
触 (touch, contact) + 媒 (intermediary, medium)
USAGE (Sense 1):
A fundamental concept in chemistry. A 触媒 enables or speeds up a reaction while remaining unchanged itself.
USAGE (figurative):
Used in news, essays, and formal writing to describe something that triggers or accelerates a process of change.