Welcome to English in a Minute, where we teach you all about idioms in American English.

欢迎收听《一分钟英语》，在这里我们将教您一些美式英语中的俚语。

Have you even heard the American English idioms...
你听过这个美式俚语么？
Once in a blue moon. It doesn't mean that the moon is blue.
Once in a blue moon（千载难逢），它的意思可不是月亮是蓝色的。
So let's listen to this American English conversation to find out how it is used:
下面让我们来听听这段美语对话，看看这个短语的用法：
Where did you say your brother lives?
你兄弟住在哪？
He lives all the way in Minnesota, so I never get to see him.
他住在明尼苏达州，但是到处搬来搬去。所以我没去看过他。
I only get to see him once in a blue moon.
我只难得有一次拜访过他。（once in a blue moon）
Once in a blue moon is a common way of saying that something does not happen often.
once in a blue moon意思是某事不经常发生，这是一个很常见的用法。
But what is a blue moon?
但是什么是蓝月亮呢？
We typically see a full moon once a month.
一般来说，我们一个月会看到一次满月。
And seeing two full moons in the same month is rare.
在一个月中出现两个满月是很罕见的。
The second full moon in a particular month is called the blue moon.
某个特别的月份中的第二个满月就叫蓝月亮。
Once in a blue moon is an informal phrase.
Once in a blue moon（千载难逢） 是一个非正式短语。
And that's English in a Minute.
以上就是本期的《一分钟英语》。