Medical compounds: 肝炎 (hepatitis), 肝脏 (liver organ), 肝癌 (liver cancer), 肝功能 (liver function). In slang, 肝 is also used as a verb meaning 'to grind' in gaming.
grammar
月 (flesh/body radical) + 干 (gān, phonetic) - a body organ pronounced gān.
Left flesh radical (Kangxi 130, the side-form of 肉). Marks 肝 as a body-part character: the liver is an organ of meat. Same radical anchors 肺 (lung), 肠 (intestine), 脾 (spleen), 胃 (stomach), 胆 (gallbladder).
Right-side 干 supplies the sound, matching the parent's gān exactly with no tone shift. The 'dry / trunk' meaning plays no role here - pure sound borrowing. Same gān series: 杆 (pole), 竿 (bamboo pole), 赶 (catch up).
