下顎[kagaku] lower jaw
二重顎[nijuuago] double chin
顎骨[agobone] jawbone
上顎[uwaago] upper jaw
顎紐[agohimo] chin strap

顎ひげ[agohige] beard (esp. on the chin)
下顎骨[kagakukotsu] mandible
顎関節[gakukansetsu] jaw joint
顎で使う[agodetsukau] to set somebody to work in an arrogant fashion