noun
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.
後頸部に痛みを感じる場合は、早めに医師に相談してください。
If you feel pain in the back of your neck, please consult a doctor promptly.
解剖学の授業で後頸部の筋肉について学んだ。
In anatomy class, we learned about the muscles of the nape.
首の後ろ is a common, non-technical phrase meaning 'back of the neck', used in daily conversation.
Compound of 後 (こう, 'back') + 頸部 (けいぶ, 'neck region'). A straightforward Sino-Japanese anatomical term.