Suppose you observed that tina had a circular area without hair on the back of her scalp. what word would best describe this?

The answer would be alopecia areata

Alopecia areata is a condition where a part of the head is losing hair. The area of alopecia areata mostly consists of a small circular spot, but it also could be spread diffusely in the head. The underlying mechanism of this disease is autoimmune where the immune cells mistakenly attack the hair cells.