Hair loss (alopecia) is categorized as scarring (with permanent destruction of hair follicles) or nonscarring.
Nonscarring alopecia is the most common form of hair loss and can be classified as patterned, diffuse, or focal, based on the distribution of hair loss.
The Journal of the American Medical Association had a helpful Patient Page on non-scarring alopecia inj August 2022. Here's the link: Download Common Causes of Baldness JAMA