Internal organs such as the heart, lungs, liver, etc. (used in medical and health contexts).
臓器移植は重い病気の患者を救う手段の一つだ。
Organ transplantation is one way to save patients with severe illnesses.
医師は患者の臓器の機能を詳しく検査した。
The doctor examined the patient's organ functions in detail.
解剖学の授業で臓器の構造を学んだ。
I studied the structure of organs in the anatomy class.