"Cloud nine" is an idiomatic expression that is often used to describe a state of extreme happiness, joy, or contentment. When someone is on "cloud nine," they are experiencing a great sense of euphoria or bliss.
The origin of the phrase is unclear, but it is believed to have originated from the scale of clouds used by meteorologists to classify different types of clouds. In this scale, "cloud nine" refers to the cumulonimbus cloud, which is the highest cloud type and often associated with thunderstorms. The idea behind the phrase is that being on cloud nine is like being on the highest cloud in the sky, symbolizing a feeling of being elevated or on top of the world.
People use the expression "on cloud nine" to describe a variety of positive experiences or emotions, such as falling in love, achieving a personal goal, receiving good news, or experiencing a general sense of happiness and contentment. It conveys a feeling of intense elation and a state of pure bliss.