阶

例句：

1. 1. The old man sat on the stairs, waiting for his grandson to come home.
   老人坐在楼梯上，等待他的孙子回家。
2. 2. The company has a three-tiered salary structure.
   这家公司有一个三级工资结构。
3. 3. She climbed up the ladder of success, one step at a time.
   她一步一个脚印地攀登成功之梯。