There are seven levels of loss in the Norwood scale:

Norwood 1
Normal head of hair with no visible hair loss.

Norwood 2
The hair is receding in a wedge-shaped pattern.

Norwood 3
Same receding pattern as Norwood 2, except the hairline has receded deeper into the frontal area and the temporal area.

Norwood 4
Hairline has receded more dramatically in the frontal region and temporal area than Norwood 3 and there is the beginnings of a bald spot at the back of the head.

Norwood 5
Same pattern as Norwood 4 but much reduced hair density.

Norwood 6
The strip of hair connecting the two sides of the head that existed in Norwood 4 and 5 no longer exists in Norwood 6.