Zi Collection, Middle Volume Radical: Mouth (kǒu) Page 283, Entry 03 Pronounced kǎo (falling tone) - same sound as 尻 (kāo). Explained in "Yùpiān" as bone. "Piānhǎi" states it is the hip bone. "Zhèngzìtōng" explains: 尻 (kāo) is the end of the spine.