Question

why does a drop of stick to the surface of the glass​

Answer 1

If you put water on glass, it forms a thin film on the surface. So, the adhesive forces between water and glass are strong enough to hold the water molecules against the surface of the glass. A water drop is present on a glass plate (in a horizontal position).

Answer 2

Answer:

Adhesion is responsible for a meniscus and this has to do in part with water's fairly high surface tension. And since water molecules like to stick together, when the molecules touching the glass cling to it, other water molecules cling to the molecules touching the glass, forming the meniscus.