Trichology is the scientific study of the hair and scalp.
Trichology is the branch of dermatology that deals with the scientific study of the health of hair and scalp. (Source: Wikipedia)
If we break the word trichology down into its component parts we can see where the name comes from:
Tri from the Greek ‘trikhos’ meaning hair
Ology, meaning the subject of a study or a branch of knowledge.