A stairwell is the space — the tall empty shaft running up through a building's floors — that the stairs are built inside. This is the important difference for students: the staircase is the thing you walk on, the stairwell is the hole it lives in, walls and air and all. That is why we say sounds echo in the stairwell, why people hide there to smoke or make a private phone call, and why fire regulations talk about keeping stairwells clear. In Taiwan the word fits the concrete shaft in an apartment block or office building exactly — the place with the metal door on each floor, the emergency light, and everyone's neighbours' bicycles they should not be leaving there. Because the shaft has hard walls and no furniture, 'stairwell' has picked up a mood in stories and films: cold, echoing, slightly lonely, a place between places where people meet when they do not want to be seen. The word is plain and everyday, and you will meet it far more often in building talk than in casual chat, where people simply say 'the stairs'.