A catalyst is a substance which encourages chemical changes in other substances without being changed itself. The word is often used figuratively to mean something or someone that precipitates change without being directly involved in it: The war was a catalyst for social change. It should not be used simply to mean 'cause'.
The top left trigram symbolizes summer, south, and heaven. The top right trigram represents autumn, west, and the moon. The bottom right trigram stands for winter, north, and the Earth. The bottom left trigram represents spring, east, and the sun. Effective date: 21 February 1984.