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Vapor is simply the American way to write . The meaning is exactly the same: a mass of very tiny drops of liquid floating in the air, usually because the liquid was heated. Steam above a hot pot, mist rising off a road after rain, the cloud you breathe out on a cold morning — all vapor. In science it also means the gas form of something that is normally a liquid or solid, as in water vapor.
Vapor is simply the American way to write vapourvapor只是美式拼法，寫的就是vapour。The meaning is exactly the same意思完全一樣：a mass of very tiny drops of liquid floating in the air就是一團懸浮在空氣中的極微小液滴，usually because the liquid was heated通常是因為液體被加熱了。Steam above a hot pot熱鍋上方的蒸氣、mist rising off a road after rain雨後路面升起的霧氣、the cloud you breathe out on a cold morning冷天早上你呼出的那團白氣——all vapor全部都是vapor。In science it also means the gas form of something that is normally a liquid or solid在科學上它也指原本是液體或固體的東西變成的氣體形態，as in water vapor就像water vapor（水蒸氣）這個詞。
Which spelling should you use? Look at where you are writing. Americans write vapor, color, flavor, honor. British, Australian, and most Hong Kong/older Taiwan school materials write , colour, flavour, honour. Taiwan English teaching leans American, so vapor is usually the safer choice here — but both are correct English, and no exam will mark you wrong for a consistent choice. What matters is not mixing them in one piece of writing.
Which spelling should you use?你該用哪種拼法呢？Look at where you are writing要看你是在哪裡寫作。Americans write vapor, color, flavor, honor美國人寫vapor、color、flavor、honor，British, Australian, and most Hong Kong/older Taiwan school materials write vapour, colour, flavour, honour英國、澳洲，還有大部分香港和台灣早期的教材則寫vapour、colour、flavour、honour。Taiwan English teaching leans American台灣的英語教學比較偏美式，so vapor is usually the safer choice here所以在這裡用vapor通常比較保險——but both are correct English但兩種拼法都是正確的英文，and no exam will mark you wrong for a consistent choice只要你前後一致，考試也不會因此把你判錯。What matters is not mixing them in one piece of writing重點是不要在同一篇文章裡混用兩種拼法。
There is also a verb, which you will meet mostly in science fiction and games: to vapor or, much more usually, — to turn something into vapor, or destroy it so completely that nothing solid is left. Two useful modern uses: water vapor is the standard term in weather and science, and vape (the electronic cigarette) is a of vapor.
There is also a verb也有一個動詞用法，which you will meet mostly in science fiction and games主要會在科幻小說和遊戲裡碰到：to vapor or, much more usually, vaporizeto vapor，不過更常見的是vaporize，to turn something into vapor意思是把東西變成蒸氣，or destroy it so completely that nothing solid is left或是把它徹底毀滅到什麼固體都不剩。Two useful modern uses有兩個實用的現代用法：water vapor is the standard term in weather and sciencewater vapor是氣象和科學裡的標準用詞，and vape (the electronic cigarette) is a shortening of vapor而vape（電子菸）就是vapor的縮寫。
組成From Middle English vapour, from Anglo-Norman and Old French vapor, from Latin vapor meaning 'steam, heat'.
原始詞典資料11 筆記錄
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
vapornoun/ˈveɪpə/
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Cloudy diffused matter such as mist, steam or fumes suspended in the air.
- A mild vapour is thrown out, and not a hot steam; the invention appears to control the amount of the vapor, and and ^([sic]) even the force of the fire which produces it.
- The desert storm was riding in its strength; the travellers lay beneath the mastery of the fell simoom.[…]Drifts of yellow vapour, fiery, parching, stinging, filled the air.
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The gaseous state of a substance that is normally a solid or liquid.
- Surprisingly, this analysis revealed that acute exposure to solvent vapors at concentrations below those associated with long-term effects appears to increase the risk of a fatal automobile accident. Furthermore, this increase in risk is comparable to the risk of death from leukemia after long-term exposure to benzene, another solvent, which has the well-known property of causing this type of cancer.
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Something insubstantial, fleeting, or transitory; unreal fancy; vain imagination; idle talk; boasting.
- For what is your life? It is even a vapour, that appeareth for a little time, and then vanisheth away.
- I am at this present very sick of my little vapour of fame.
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datedAny medicinal agent designed for administration in the form of inhaled vapour.
- Sulphurous fumes have also been recommended, as well as diffusing a variety of vapors in the apartment of the patient; on their beneficial or injurious effects we are unable to speak.
- Hence the vapor, so useful in expanding the compressed tissues and enabling the air to permeate and expand the contracted parenchyma in consumption, causes a sensation of great fatigue in asthma.
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archaicHypochondria; melancholy; the blues; hysteria, or other nervous disorder.
- Jan 13, 1732, John Arbuthnot, letter to Jonathan Swift He talks me into a fit of vapours twice or thrice a week.
- She made several gulps and controlled her breath. She released her grip on Podson and stared at him without recognition. Podson went on patting her reassuringly, relieved from administering first aid to an attack of the vapours.
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obsoleteWind; flatulence.
- The surcharge of the stomack from a gross vapour, and from the poise of some outward weight, are alike
vaporverb/ˈveɪpə/
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To become vapor; to be emitted or circulated as vapor.
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To turn into vapor.
- to vapor away a heated fluid
- He'd […]laugh to see one throw his heart away, / Another, sighing, vapour forth his soul.
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To emit vapor or fumes.
- Running waters vapour not so much as standing waters.
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To use insubstantial language; to boast or bluster.
- He vapoured, and fretted, and fumed, and trotted up and down, and tried to make himself pleasing in Miss Hollis's big, quiet, grey eyes, and failed.
- then the Major gave us a graphic account of a struggle he had with a wounded bear. I privately wished that the bears would win sometimes on these occasions; at least they wouldn't go vapouring about it afterwards.
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To give (someone) the vapors; to depress, to bore.
- “I only mean,” cried she, giddily, “that he might have some place a little more pleasant to live in, for really that old moat and draw-bridge are enough to vapour him to death […].”
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。