field

a piece of land cleared of trees and usually enclosed

he planted a field of wheat

a region where a battle is being (or has been) fought

they made a tour of Civil War battlefields

somewhere (away from a studio or office or library or laboratory) where practical work is done or data is collected

anthropologists do much of their work in the field

a branch of knowledge

in what discipline is his doctorate?

the space around a radiating body within which its electromagnetic oscillations can exert force on another similar body not in contact with it