If two residents share a room, which furniture item must be shared?

In a scenario where two residents share a room, the bedside table, commonly referred to as a nightstand, is the furniture item that is typically shared. This item serves a functional purpose by providing both residents with easy access to personal items such as lamps, books, or other essentials that they may wish to have within arm's reach while in bed.

The other furniture items listed have different implications when it comes to shared living arrangements. A bed is generally designed for one person at a time, and having shared sleeping arrangements can vary significantly based on the comfort and preferences of the individuals. A cupboard can be separately assigned to each resident for organizing personal belongings, and a window does not constitute furniture in the same sense but rather is part of the room's structure and overall living environment.

Thus, the nightstand stands out as the essential shared piece of furniture that supports the needs of both individuals living in the same space.