Several parts combine into one character.

肘 is a semantic compound: 月 (flesh radical) + 寸 (cùn, "inch / a hand's-breadth"). 寸 originally pictured "the joint just below the wrist" — the body's natural unit of measurement. So the etymology is unusually precise: "the joint of the arm at the body's measurement point = elbow." A character whose construction maps directly to anatomy.

Korean reading "ju." 肘關節 (ju-gwanjeol, elbow joint — medical). Very narrow Korean usage — the Hangul word (palkkumchi) dominates daily speech, and 肘 appears almost only in anatomy textbooks and acupuncture-meridian charts.

Mandarin zhǒu, 3rd tone. 肘 (zhǒu, elbow — daily), 肘子 (zhǒuzi, elbow — but also "pork hock / pig knuckle" in cooking contexts). The cooking sense is alive across Chinese menus: 红烧肘子 (hóngshāo zhǒuzi, braised pork hock) is a banquet staple where the cut's name comes directly from its anatomical position on the pig.

Japanese on-reading チュウ (chū) — almost never used. Kun-reading ひじ (hiji) — 肘 (hiji, elbow — daily), 肘掛け (hijikake, armrest — common in furniture vocabulary), 肘鉄砲 (hijiteppō, "elbow gun" = an elbow-jab to refuse advances — a slangy Japanese phrase for rejecting a romantic approach: 肘鉄を食らう, "to be hit with the elbow gun" = "to be rejected").

Memory aid: flesh (月) plus the inch-mark (寸) — the body part at the arm's measuring joint.