Translation guide
The part of the body connecting the head and torso, and related concepts like the neck of an object or a narrow part.
The physical neck of a person or animal.
The most common and general word for 'neck' in Japanese. Used for both people and animals.
首が痛い。
My neck hurts.
A giraffe's neck is long.
The part of a garment that surrounds the neck, like a collar or neckline.
The slender part of something, like a bottle or a musical instrument.
To be fired from a job (idiomatic, related to 'neck' as in 'get the axe').
The front part of the neck, including the throat, often in medical or choking contexts.
A narrow strip of land, such as an isthmus or a peninsula neck.
首 (くび) is the body part, while 襟 (えり) is the collar of clothing. Using 首 for a shirt collar sounds odd.
The phrase 首になる (to be fired) is extremely common and should be learned as a set phrase. It does not literally mean 'to become a neck' in modern usage.
V-neck sweater
Bottleneck
社長は彼の首を切った。
The boss fired him.
Neck of the peninsula