Conditions

First, let's get some terminology out of the way.  Alopecia just means "hair loss".  It isn't on its own a diagnosis and doesn't really help us figure out possible causes, it's just a descriptive term.

 

The most common condition affecting men's hair is Androgenetic Alopecia (genetic/hereditary/familial male pattern baldness).

Women's hair loss often needs more investigation to figure out the most likely causes, but women may also be affected by hereditary hair loss.