According to Merriam-Webster Unabridged Dictionary: Air-conditioning, when used as a noun, is hyphenated. The house has air-conditioning. Air conditioner, a noun, is open. The air conditioner is on the fritz. Air-conditioned: Both as an adjective and a verb is hyphenated. The air-conditioned room. Air-condition a building. The above article is an update. Back when I originally wrote this article (June 14, 2013), […]
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