noun
Refers broadly to a person who administers treatment, especially in medical, psychological, or therapeutic contexts. Can be used for doctors, counselors, or alternative healers.
彼女は心の傷を癒やす治療者として知られている。
She is known as a therapist who heals emotional wounds.
その治療者は患者に新しい薬を試した。
The clinician tried a new medication on the patient.
セラピスト is a loanword often used for counselors or physical therapists, whereas 治療者 is a broader, more formal term that can also refer to physicians.
Compound of 治療 (treatment) and 者 (person). The reading is standard on'yomi.