upstairs
UK: ʌpˈsteəz | US: ʌpˈsterz
adv. on or to a higher floor of a building
adj. located on a higher floor
n. the upper floor(s) of a building
The word "upstairs" combines "up," from Old English "ūp" (indicating upward direction), and "stairs," derived from Old English "stǣger" (a flight of steps). The compound emerged in Middle English (14th century) to describe movement or location toward higher floors via stairs. Its logic reflects spatial progression—physically ascending steps to reach an elevated level. Over time, it gained adverbial, adjectival, and nominal uses while retaining its core spatial meaning.
She ran upstairs to fetch her jacket.
The upstairs neighbors are unusually quiet today.
The cat hid upstairs during the storm.
The office is located upstairs, next to the conference room.
They converted the upstairs into a rental apartment.