恒量的英文：
constant
adj. 固定的；不停的，接连不断的
n. 常数；不变的事物
Matter is in constant motion and constant change.
物质总是在不断运动，不断变化的。
A constant guest is never welcome
常客令人厌
The market is in a constant state of flux.
市场行情在不断变化。
The market is a stream that is in constant motion.
市场像河流一样不断地波动。
The speed of light is an invariant constant.
光速是一个不变常数。