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neck
head
dismissal (from a job); firing; sacking
「首」 has other readings with different meanings.
首が痛くて動かせません。
My neck hurts and I can't move it.
不思議な話を聞いて首をかしげた。
I tilted my head at the strange story.
首がとても痛くて辛いです。
My neck hurts a lot and it's painful.