noun
stethoscope
Medical instrument for listening to internal body sounds, such as heart and lung sounds.
医者は聴診器で患者の心音を聞いた。
The doctor listened to the patient's heart sounds with a stethoscope.
Compound of 聴 (chō, 'listen') + 診 (shin, 'examine') + 器 (ki, 'instrument'). A straightforward Sino-Japanese medical term.