"upstairs" in the noun sense
1. upstairs
the part of a building above the ground floor
"no one was allowed to see the upstairs"
"upstairs" in the adjective sense
1. upstairs, upstair
on or of upper floors of a building
"the upstairs maid"
"an upstairs room"
"upstairs" in the adverb sense
1. upstairs, up the stairs, on a higher floor
on a floor above
"they lived upstairs"
2. upstairs
with respect to the mind
"she's a bit weak upstairs"
Source: WordNet® (An amazing lexical database of English)
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