Several parts combine into one character.

Phonetic-semantic compound: 月 (flesh-radical) + 要 (important / essential, from earlier batch — providing both phonetic value and semantic suggestion). The encoded meaning: "the most essential part of the body" → waist / lower back. The character literally says: "this body part is what holds you together." This etymological reading reflects East Asian medical wisdom: lower back health was considered foundational to physical strength. Identical across 繁體 / 新字体 / 简体.

Notice the recursion: 要 (the previous character meaning "important") originally meant "waist" itself (from a pictograph of hands on hips) — when the meaning generalized to "important / essential", a new character 腰 was created (with 月 added) to recover the original "waist" meaning. So 要 and 腰 are sibling characters preserving etymological history: one became abstract "essential", the other kept the body-part meaning.

Mandarin: yāo, level 1st tone. 腰 (yāo, waist), 腰部 (yāobù, lumbar region), 腰带 (yāodài, belt — "waist-band"), 腰围 (yāowéi, waist measurement), 弯腰 (wānyāo, to bend at the waist), 腰果 (yāoguǒ, cashew — "waist-fruit", from the kidney shape). 弯腰 (bowing at the waist) is the everyday Chinese verb for the formal Japanese-style bow.

Japanese: on-reading ヨウ (yō) — 腰痛 (yōtsū, lower back pain — extremely high-frequency Japanese health complaint). Kun-reading こし (koshi) is the everyday word — 腰 (koshi, lower back / waist / hip), 腰掛ける (koshikakeru, to sit down / lean — formal verb). Japanese folk wisdom and martial arts traditions emphasize 腰 as the body's power center — 腰の力 (koshi no chikara, "strength of the lower back") in budo / sumo / kendo.

The Japanese 腰痛 (yōtsū, low-back pain) is treated as a major lifestyle ailment — desk workers in Japan are especially prone to it, and 腰痛体操 (yōtsū taisō, low-back exercise) is widely practiced.

Memory aid: flesh + essential = the body's most essential part — the lower back / waist.