首先发布的是狭义相对论，它的基础是对于任何一个人来说，光速是恒定不变的。

Special relativity came first and is based on the speed of light being constant for everyone.

youdao

尼尔森(Nielsen Online)做了很多工作来衡量网络通信的水平，并声称这些数字全年保持恒定不变。

Nielsen Online does a great deal of work in measuring levels of Internet traffic, and has stated that these Numbers have been constant for a full year.

youdao

就假定保持a恒定不变。

Let's say keep a constant.

youdao