Dogs don’t understand words or language. As fellow mammals, they share enough of our life experience that they can easily tune in to our feelings and wishes.
Mine understand words. Out, walk, ride, go, they’ll grab their leash in their mouth and run to the door. Other words understood, nap, sleep, they go to their beds. Ball, toy, frisbee, they get excited and go get them. Bath, the water breed jumps in the tub. The hound will slink off and hide.