What is the term for trim around a doorway or window?

The term for trim around a doorway or window is “casing.” Casing serves both a functional and aesthetic purpose; it frames the opening and provides a transition between different materials, such as the wall and the door or window. It also helps to cover the gap between the frame of the door or window and the drywall, creating a polished appearance.

Baseboard, while also a type of trim, is located at the junction of the wall and the floor, serving to cover the joint and protect the wall from damage. Crown molding, on the other hand, is a decorative trim that is installed at the junction of the walls and ceiling, adding visual interest to the upper edges. Chair rail is a horizontal decorative molding typically installed around the perimeter of a room at a height that protects walls from damage caused by chairs. Each of these terms refers to a different type of trim and their respective locations in a building's interior.