in ‧ door /ˈɪndɔː $ -ɔːr/ BrE AmE adjective [only before noun]
used or happening inside a building OPP outdoor :
an indoor swimming pool
the world indoor athletics championship
Too much central heating can harm indoor plants.
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GRAMMAR
indoor, indoors
Indoor is an adjective and indoors is an adverb:
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I stayed indoors (NOT indoor).
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indoor sports (NOT indoors sports)