Four periods a week.

每星期有四节课。

youdao

The process can be divided into four periods.

其演进过程大致可以分为四个时期。

youdao

I 've been teaching four periods this morning.

今天上午我已教了四节课。

youdao

We've probably had four major periods in American history of there's one other picture I wanted to put up.

在美国历史上,我们大约经历了四个时期,在我想贴的另一张图片上

耶鲁公开课 - 美国内战与重建课程节选

We have probably four great reform periods in American history.

我们美国历史上约有四个大改革时期

耶鲁公开课 - 美国内战与重建课程节选

With the new regimen, called Seasonale, women would take the pill for 84 consecutive days and have four periods a year.

CNN: Emerging contraceptive options

We identified four periods, highlighted in yellow, which experienced clear rate increases.

FORBES: Buffett Is Right, Bonds Need A Warning Label

In those areas that have had three or four periods of experimental burning only half the number of species of tree seedlings originally found are still there.

ECONOMIST: A new experiment is setting the Amazon on fire