医 (Kanji for doctor)

Onyomi

I am a medical doctor, who surgically removes an arrow out of your colon and puts it in the biohazard container.

医者(いしゃ)	doctor ★★★☆☆ 医 (doctor) + 者 (professional) = 医者 (doctor) doctor
歯医者(はいしゃ)	dentist ★★☆☆☆ 歯 (tooth) + 医者 (doctor) = 歯医者 (dentist)
医師(いし)	doctor ★☆☆☆☆ NP 医 (doctor) + 師 (master, teacher) = 医師 (doctor) a more formal word for doctor -(you wouldn't say "I need to see the 医師!" - you'd say, "I need to see the 医者（いしゃ）！”）
XXX 医(い)	-ology ★☆☆☆☆ SUF a SUFFIX meaning, 'XXX branch of medicine -' in other words, 'XXXology'.
医療(いりょう)	medical treatment ★☆☆☆☆ 医 (doctor) + 療 (medical therapy) = 医療 (medical treatment) medical treatment- the kind one gets in a hospital (x-rays, MRI, surgery, etc.)