English Idiom – Once in a blue moon.
Very rarely or almost never. If something happens once in a blue moon it happens very infrequently.
The blue moon in this expression has nothing to do with the colour blue. In astronomy a blue moon is the third full moon in a season of four full moons. Seasons (in astronomy) are 3 months long so a fourth moon in a season is a rare event – actually about once every 3 years.
If you are feeling blue (idiom) it means that you are feeling sad.
Example:
- “I just bought myself a fancy new coffee maker. I don’t know why, I only drink a cup of Joe once in a blue moon!”
In the News
Spotted in the newsFisherman’s special lobster find is once in a blue moonbelfasttelegraph.co.ukWhat is an idiom?
An idiom is a word or phrase that is not taken literally. An idiom is an expression that cannot be understood from the meanings of its individual words, but has a separate meaning of its own.
Frequently Asked Questions
It means very rarely or almost never — if something happens once in a blue moon, it happens very infrequently.
In astronomy, a blue moon is the third full moon in a season that has four full moons, which happens roughly once every three years — it has nothing to do with the colour blue.
No — “feeling blue” is a different idiom that means feeling sad.
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