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医者は患者を診察した。
The doctor examined the patient.
A qualified practitioner of medicine who diagnoses and treats illnesses.
医者に診てもらった方がいいよ。
You should see a doctor.
この病院には優秀な医者がたくさんいる。
This hospital has many excellent doctors.
Refers to a licensed medical professional, not a medical student or nurse.
医者 is the general term for a doctor, while 医師 is the legal/official title. All 医師 are 医者, but not all 医者 are 医師 (e.g., medical students or retired doctors may not hold the title).
From 医 (medical treatment) + 者 (person). The kanji 医 originally depicted a person administering acupuncture or moxibustion.
医者 is the most common term for a doctor in everyday speech. 医師 is more formal and often used in legal or professional contexts. ドクター is a loanword from English, used casually.