flight of stairs

n. 阶梯步级

例句与用法：

The old woman fell down a flight of stairs.

那位老太太从一段楼梯上摔了下来。

She died when she was ninety, not of old age, but from head injury when she fell down a flight of stairs.

她90岁时去逝，并不是老死，而是从楼梯上摔下来头部受伤而死。