By which process are clouds dew and fog formed

Condensation. The water that evaporates into the sky gets condensed into clouds. For the dew,

"Dew is water in the form of droplets that appears on thin, exposed objects in the morning or evening due to condensation. As the exposed surface cools by radiating its heat, atmospheric moisture condenses at a rate greater than that at which it can evaporate, resulting in the formation of water droplets."