nape; back of the neck
Anatomical term for the posterior region of the neck. Used in medical or formal contexts; in everyday speech, うなじ or 首の後ろ is more common.
If you feel pain in the back of your neck, please consult a doctor promptly.
In anatomy class, we learned about the muscles of the nape.
Compound of 後 (こう, 'back') + 頸部 (けいぶ, 'neck region'). A straightforward Sino-Japanese anatomical term.