Stomata are small specialized passages for water and gases present in the epidermis of plants. as the plant needs more or less water the stomata respectively open or close, allowing or preventing the passage of gases by diffusion. what is the name of the process in which plants lose water to the atmosphere in the form of vapor?

Transpiration is the process in which moisture is carried through plants from roots to little pores on the bottom of leaves, where it changes to vapor and is discharged to the atmosphere.
Leaf surfaces are dotted with pores called stomata. It is a tiny opening or pore that is used for gas exchange. They are mostly found on the under-surface of plant leaves.