Cohesion

In this picture you can see that while it began to rain, the rain began to join together forming droplets on the windshield. This is because of the process of cohesion.

Cohesion, like adhesion is a form of attraction between one or more objects or surfaces, but cohesion relies on two similar or identical objects in order for them to stick together. A common form of cohesion that we see almost every day is the forming of water droplets whether it be from morning dew, in the shower, or a rainy day. These water droplets are formed through the process of cohesion as tiny water molecules begin to attract and clump together forming these larger molecules of water.

Sources:
Mrs. Beethe's notes.