Clouds and Rain .
云和雨。
Water moves from place to place.
水从一个地方流到另一个地方。
Water moves from the earth to the air and back again.
水从地球流到空气，然后再流回来。
This is called the water cycle.
这被称为水循环。
The sun makes water warm.
太阳使水变热。
Then the water evaporates or changes into water vapor.
然后水蒸发或变成水蒸气。
We cannot see water vapor.
我们看不到水蒸气。
Water vapor goes up into the air.
水蒸气上升到空气中。
Water vapor cools in the sky.
水蒸气在天空中冷却。
Then water vapor condenses or changes into tiny water drops.
然后水蒸气凝结或变成微小的水滴。
Many drops of water form clouds.
许多水滴形成云。
Water drops in the clouds get bigger and bigger.
云中的水滴越来越大。
They then fall back to the earth as rain or snow.
然后它们以雨或雪的形式落回地球。
The rain or snow falls into rivers, lakes, and oceans.
雨或雪落入河流、湖泊和海洋。
And the water cycle continues.
水循环还在继续。