Question

why a water droplet is in spherical shape

Answer 1

this arrangement is done to reduce surface tension. for a given volume sphere has the least surface area.

Answer 2

Surface tension is responsible for the shapeof liquid droplets. Although easily deformed,droplets of water tend to be pulled into aspherical shape by the cohesive forces of the surface layer. In the absence of other forces, including gravity, drops of virtually all liquids would be approximately spherical