Vapor

Part of speech: noun, verb

Pronunciation: /ˈveɪpə/

Definitions

1. A substance in gas form that is typically liquid or solid at room temperature, such as steam or mist
2. A gaseous state of a substance that would normally exist as a liquid or solid under standard conditions, often visible as a cloud or haze
3. A form of matter transitioning from liquid or solid to gaseous state, frequently observed in the atmosphere as fog or steam

Etymology: The American spelling "vapor" is the one that most readers meet first, yet the word came into English in its British form, "vapour," through Middle English, and the spelling only split later. Its ultimate source is Latin "vapor," meaning steam or heat, which passed into English by way of Anglo-Norman and Old French "vapeur" and "vapor." Ancient Latin speakers used it for the warm breath or exhalation rising from something heated, and that sense of rising warmth still sits behind the modern meaning of a gas that hangs in the air. The word has a deep Indo-European ancestry: Latin "vapor" traces back through Proto-Italic to a much older root, but this belongs to the word's prehistory rather than its life in English. Its English story is mostly one of a steady narrowing. Medieval writers used it for any airy exhalation or mist, and the verb sense of giving off vapour followed the noun. The modern American spelling "vapor" reflects the common American preference for dropping the final "u" in words like "colour" and "humour."

Synonyms: steam, mist, fog, fume, gas

Antonyms: solid, liquid