记忆力不常使用就会衰退。

Memory can atrophy through lack of use.

《牛津词典》

我周末大多都能见到她，但平时不常见到。

I see her most weekends but not very often in between.

《牛津词典》

幸运的是，年轻妇女患乳腺癌的情况不常见。

Fortunately, cancer of the breast in young women is uncommon.

《柯林斯英汉双解大词典》

If they have an underperforming fund, sometimes they allow it to die a dignified death; although, that doesn't happen very often.

如果他们旗下有一支表现不佳的基金,他们可能会让基金退市,当然这种情况不常发生

耶鲁公开课 - 金融市场课程节选

It gives a little bit more excitement to your weekend, something different to do than the usual thing.

去做些你不常做的事，这会为你的周末增添更多精彩。

如何利用空闲时间 - SpeakingMax英语口语达人

So, don't start here. And, it happens infrequently, but I've got to tell you, a few years back on the final exam, a couple of people were involved in passing information back and forth.

不要开始这样做，这也不常发生，我要告诉你们,几年前的期末考试里，有几个人，他们,给前后传递答案。

麻省理工公开课 - 固态化学导论课程节选