Alopecia is the medical term for baldness. The word has an interesting linguistic derivation, and comes from the Greek word Alopex, meaning fox. Foxes in Hippocrates time apparently were afflicted by hair loss from mange.
Men and women have different kinds of hair loss. In men, there is the receding hairline with age. As women age, there’s some thinning of the hair generally, and at the top of the head.

A special kind of hair loss that occurs in discrete areas is called alopecia areata. This is an auto immune disease, and is increased in frequency with people who have other autoimmune diseases. Hair loss can also be due to a fungal disease (ringworm) especially in children.
Cancer treatment can cause generalized hair loss, and we have all seen the bald children receiving cancer therapy, especially radiation.
Hair loss and regrowth comes in cycles. We all lose many hairs each day, but they regrow. When the cycle slows, there is a net loss of hair.
When I was in medical practice, my partner had early onset baldness, and was given hair transplants, which were effective. Treatments include minoxidil, which apparently increases the speed of hair cycles. An irritant, such as anthralin, will sometimes help Alopecia areaway by causing inflammation, apparently resetting the immune reaction that’s causing the hair loss.
Finasteride, which interferes with local testosterone production, can stimulate hair growth. I take Finasteride for prostate enlargement, and was surprised to hear about it’s effect on hair growth. Maybe that’s why I have such a bushy head of hair.
Please read the following at Mayo clinic article for a more organized discussion.