Question

What is cloud ? How it form in the sky .

Answer 1

Clouds are moving in sky

clouds are formed by the evaporation

Answer 2

A mass of very small drops of water that floats in the sky and is usually white or grey is called clouds

Clouds form when rising air, through expansion, cools to the point where some of the water vapor molecules "clump together" faster than they are torn apart by their thermal energy. Some of that (invisible) water vapor condenses to form (visible) cloud droplets or ice crystals.