on and off

例句：

1. Since most of them have never had an opportunity to use computer, the training began with turning on and off the computer. Basic computer and Internet skills were the main courses offered, according to the trainer.
   據負責培訓的老師介紹，由於這些女教師大多數從來沒接觸過電腦，所以培訓班將從開關機器教起，主要進行計算機基本操作和網路知識的講座以適應不同學員的水平。
2. It rained on and off all day.
   整天斷斷續續地下著雨。

英文解釋：

副詞 on and off:

1. not regularly
   同義詞：off and on