noun
Anatomical term for the jawbone or jaw area. Often used in medical or formal contexts; in everyday speech, あご is more common.
顎の骨を骨折した。
I fractured my jawbone.
顎関節症で口が開けにくい。
I have trouble opening my mouth due to temporomandibular joint disorder.
Rarely used kanji form.
あご is the common everyday word for 'jaw' or 'chin'. 顎 (がく) is a more technical, anatomical term used mainly in medical contexts.
The kanji 顎 is a phono-semantic compound with 各 (phonetic) and 頁 (head), originally referring to the jaw. The reading がく is the on'yomi.