When two things that are alike stick together, they cohere. Water molecules in a cloud cohere to each other forming a droplet of water. More of these droplets cohere to each other forming larger droplets. When the cloud becomes saturated with water droplets it rains.
When two (or more) different things stick together, they adhere. When you get caught in a downpour and your clothes gets really wet, the water makes your clothes adhere (stick) to your skin.