sagging

例句：

1. 1.The roof of the house sags when it rains heavily.
   当大雨倾盆时，房子的屋顶会下陷。
2. 2. The old car sags as it ages.
   这辆旧车随着时间老化而下沉。
3. 3.The weight of the snow caused the trees to sag in the wind.
   雪的重量使树木在风中下陷。