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indoor

American  
[in-dawr, -dohr] / ˈɪnˌdɔr, -ˌdoʊr /

adjective

  1. occurring, used, etc., in a house or building, rather than out of doors.

    indoor games.


indoor British  
/ ˈɪnˌdɔː /

adjective

  1. of, situated in, or appropriate to the inside of a house or other building

    an indoor tennis court

    indoor amusements

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of indoor

1705–15; aphetic variant of within-door, originally phrase within ( the ) door, i.e., inside the house

Explanation

Use the adjective indoor to describe something that happens or is used inside a building or house. Your indoor furniture is probably a little fancier than your plastic outdoor furniture. Indoor sports are the ones you play inside, like ping pong and floor hockey — beach volleyball is not an indoor sport. Your indoor voice is likewise the one you use in your house or classroom, a quieter voice than when you holler across a parking lot to your friend in his convertible. Indoor, which has been used since the 18th century, is a shortened form of the phrase within door.

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