IPA: //kɒzˈmɛtɪʃən//
KK: /kɑːzməˈtɪʃən/
A person who is trained to apply beauty products and provide skincare treatments.
She went to the cosmetician for a facial treatment before her wedding.
Cosmetician is formed from "cosmeticos" (from Greek, meaning skilled in the use of cosmetics) and the suffix "-ian" (meaning relating to or one who). The word refers to a person skilled in the application of cosmetics or beauty treatments.
Think of someone who is 'skilled in cosmetics' — that's what a cosmetician does.