THE IDIOM COLLECTION LEARN & PRACTISE
Once in a blue moon
Understand the meaning. See it in context. Make it yours.
01 / UNDERSTAND
Meaning in plain English
Something that happens very rarely.
Usage note: keep in mind
Once in a blue moon is an informal way to say very rarely. It is not a precise timetable. Place it naturally at the beginning or end of a sentence, and avoid using it for an event that happens regularly every week.
02 / SEE IT IN CONTEXT
The expression in a sentence
- We go out for dinner once in a blue moon, since we’re always busy with work and kids.
03 / CHECK YOUR UNDERSTANDING
Quick idiom quiz
Try the two questions without looking back, then write a sentence of your own. You can retry as often as you like.
0 of 2 checked correctly
Review the meaning
Something that happens very rarely.
2. Can you recall the expression?
Complete the example using the expression from this lesson.
We go out for dinner ________, since we’re always busy with work and kids.
Show the answer
Once in a blue moon — Something that happens very rarely.
Try your own sentence (optional)
Make it yours
Write one sentence using “Once in a blue moon” about your own life.
Check your sentence
Does your sentence match this meaning?
Something that happens very rarely.
Compare: We go out for dinner once in a blue moon, since we’re always busy with work and kids.
Check the spelling and how the expression fits the sentence. Your example can be different.
Self-review only. Your sentence is not automatically marked, saved or submitted.
This quiz is for practice. To save lesson completion on this device, complete the checks in the app.
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More ways to understand and use it
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More examples in context
- We eat at that expensive restaurant once in a blue moon.
- Once in a blue moon, our old school friends manage to meet in person.
Check your understanding
If someone says they watch television once in a blue moon, do they mean every night, occasionally but rarely, or at a fixed monthly time?
Check your answer
Occasionally but rarely. The expression describes low frequency without giving an exact number of days or months.
Use it in your own words
Write one new situation where once in a blue moon fits. Explain the situation in plain English first, then rewrite it using the expression. Check that the tone and meaning suit your audience.