Is 'on cloud nine' formal or informal?

It is informal and conversational. It works well in everyday speech and casual writing, but in a formal email or business report, use 'extremely happy' or 'elated' instead.

Is it 'on cloud nine' or 'in cloud nine'?

Always use 'on' — 'I'm on cloud nine.' The preposition 'in' is incorrect with this idiom and will sound unnatural to native speakers.

What is the difference between 'on cloud nine' and 'over the moon'?

Both mean very happy, but 'over the moon' is more common in British English, while 'on cloud nine' is more common in American English. They are interchangeable in most contexts.

Can 'on cloud nine' describe someone else, or only yourself?

You can use it for anyone — 'She is on cloud nine,' 'They were on cloud nine after the wedding.' It works for first, second, and third person equally.

← Dictionary

on-cloud-nine

/ɒn ˌklaʊd ˈnaɪn/

Idiom

idiom

If you are on cloud nine, you feel extremely happy and excited. Something very good has happened, and you feel as if you are floating at the highest possible point.

She was on cloud nine after receiving the job offer.
He's been on cloud nine since his team won the final.
Getting that scholarship put her on cloud nine for days.

Adinary Nuance

The number nine carries special weight in this idiom's history. In the US Weather Bureau's International Cloud Atlas, clouds were numbered one through nine, and cloud nine — the cumulonimbus — was the tallest, most awe-inspiring formation in the sky. Being "on" it meant you couldn't go any higher. A parallel tradition exists in "seventh heaven," drawn from Islamic and Jewish cosmology, where the seventh heaven is the highest realm of divine bliss — showing how many cultures use a specific numbered level in the sky to mean perfect happiness. A competing theory traces "cloud nine" to a 1950s American radio drama where characters knocked unconscious were transported to a dreamy, floaty "cloud nine" — reinforcing the sense of blissful unreality. Whatever the true root, the number itself is part of the magic; "cloud eight" or "cloud ten" simply don't carry the same feeling.

In other languages

Vietnamese: vô cùng hạnh phúc
Spanish: en el séptimo cielo
Chinese: 欣喜若狂
Japanese: 最高に幸せ
Korean: 극도로 행복하다

Etymology

The phrase most likely comes from the US Weather Bureau's mid-20th-century cloud classification system, where "cloud nine" — the towering cumulonimbus — was the highest and most dramatic cloud type, reaching up to 40,000 feet. The idiom entered popular American English in the 1950s, with the number nine symbolising the ultimate high point.

Common phrases

be on cloud ninefeeling on cloud nineput someone on cloud ninewalking on cloud nine

Synonyms

over the moon in seventh heaven on top of the world elated ecstatic

Frequently asked questions

Is 'on cloud nine' formal or informal?: It is informal and conversational. It works well in everyday speech and casual writing, but in a formal email or business report, use 'extremely happy' or 'elated' instead.
Is it 'on cloud nine' or 'in cloud nine'?: Always use 'on' — 'I'm on cloud nine.' The preposition 'in' is incorrect with this idiom and will sound unnatural to native speakers.
What is the difference between 'on cloud nine' and 'over the moon'?: Both mean very happy, but 'over the moon' is more common in British English, while 'on cloud nine' is more common in American English. They are interchangeable in most contexts.
Can 'on cloud nine' describe someone else, or only yourself?: You can use it for anyone — 'She is on cloud nine,' 'They were on cloud nine after the wedding.' It works for first, second, and third person equally.