语言学习的根本法则就是“用进废退”。

One fundamental rule of language learning is: "Use it, or lose it. ""

youdao

但不论细节如何，这种“用进废退”的情形显然确凿无疑。

Regardless of the details, though, this would appear to be a clear case of "use it or lose it".

youdao

脑运动有：用进废退、适度用脑、整体开发、身心互动和脑体交替等规律。

The principle of brain movement have: Progress on use and retarding on waste, moderate use integral exploit, physical and mental alternation.

youdao