Vapour is a mass of very small drops of liquid hanging in the air. Most often it is there because the liquid was heated — the steam over a pot of soup, the white cloud above a bathtub, the breath you can see on a cold January morning in Taipei.

Vapour is a mass of very small drops of liquid hanging in the airVapour指的是懸浮在空氣中、由許多極小水滴組成的一團東西。Most often it is there because the liquid was heated它最常出現的原因是液體被加熱了 — the steam over a pot of soup比如一鍋湯上方的蒸氣, the white cloud above a bathtub浴缸上方的白色霧氣, the breath you can see on a cold January morning in Taipei還有台北一月寒冷早晨你看得見的哈氣。

In science, vapour also means the gas form of something that is normally liquid or solid: water vapour is water in the air, invisible when it is well mixed, visible when it gathers into drops.

In science在科學上, vapour also means the gas form of something that is normally liquid or solidvapour也指某樣通常是液態或固態的東西的氣體形態: water vapour is water in the airwater vapour就是空氣中的水, invisible when it is well mixed混合均勻時是看不見的, visible when it gathers into drops當它聚成水滴時就看得見了。

This is the British spelling. Americans write vapor. Both are completely correct; just don't switch between them inside one essay.

This is the British spelling這是英式拼法。Americans write vapor美式則拼作vapor。Both are completely correct兩種都完全正確; just don't switch between them inside one essay只是不要在同一篇文章裡兩種混用。

A point students find surprising: the white cloud you see over a kettle is not really the vapour. True water vapour is invisible. What you see is the vapour cooling and turning back into tiny drops. So strictly, the visible white is condensed vapour — but nobody will correct you in ordinary speech for pointing at it and saying vapour.

A point students find surprising一個學生常常覺得意外的重點: the white cloud you see over a kettle is not really the vapour你在水壺上方看到的那片白色雲霧其實不是真正的vapour。True water vapour is invisible真正的水蒸氣是看不見的。What you see is the vapour cooling and turning back into tiny drops你看到的是水蒸氣冷卻後又變回小水滴的樣子。So strictly所以嚴格來說, the visible white is condensed vapour看得見的那片白是凝結後的水蒸氣 — but nobody will correct you in ordinary speech for pointing at it and saying vapour但日常說話時指著它說vapour，不會有人糾正你。

The word is mostly uncountable: some vapour, a lot of vapour. Scientists do say "vapours" when they mean several different kinds, especially chemical ones, and "toxic vapours" is a common phrase on warning labels.

The word is mostly uncountable這個字大部分時候是不可數的: some vapour一些vapour, a lot of vapour很多vapour。Scientists do say "vapours" when they mean several different kinds但科學家在指好幾種不同的種類時，真的會說"vapours", especially chemical ones尤其是化學物質, and "toxic vapours" is a common phrase on warning labels而"toxic vapours"（有毒氣體）也是警告標示上常見的說法。

A useful compound: vapour trail — the long white line a plane leaves behind it in the sky.

A useful compound一個實用的複合字: vapour trailvapour trail（凝結尾） — the long white line a plane leaves behind it in the sky就是飛機在天空中留下的那條長長白線。