瓶子本身的那一段窄口
這一家就是字面上的東西，也是整個字的圖畫來源。
noun · B2
The narrow part at the top of a bottle, where the glass becomes thin and the drink pours out.
瓶頸（瓶子的窄口）
核心畫面
Picture a wide bottle tipped over. The body holds a lot, but everything inside has to leave through one thin neck, a little at a time. Nothing about the body matters while the neck is doing the deciding. Every other use of this word keeps that shape: a wide flow, one narrow place, and a line of things waiting their turn to get through it.
可以想成一個寬寬的瓶子被倒過來。瓶身裝得再多，東西都只能從上面那一段細細的窄口一點一點出去。只要窄口在那裡，瓶身有多…更多收起
可以想成一個寬寬的瓶子被倒過來。瓶身裝得再多，東西都只能從上面那一段細細的窄口一點一點出去。只要窄口在那裡，瓶身有多大就不重要了。這個字的每一個用法都保留著這個形狀：前面很寬、中間有一個窄點、後面排著一列等著通過的東西。不管是車、是檔案、還是等人簽名的公文，畫面都一樣。From the word’s history
Wiktionary records the word as bottle + neck: the narrow part at the top of a bottle. The physical object came first, and the modern uses all borrow its shape.
Wiktionary 記錄這個字是 bottle（瓶子）加 neck（脖子）組成的，本來就指瓶子上面那一段窄口。所以它先是一個看得見的東西，後來的用法才把這個形狀借去講路和流程。
Wiktionary entry 'bottleneck' (kaikki:3f6f69a190036ae4:888276338), etymology_text: 'From bottle + neck.'
Three branches
路上的那一個窄點
把馬路想成瓶子：路面是瓶身，橋或隧道是瓶口。車多的時候，能不能過就由那一小段決定。
noun · B2
A narrow part of a road where too many vehicles have to squeeze through, so the traffic backs up and drivers are held up.
交通瓶頸路段
流程裡最慢的那一關
把一件工作想成瓶子裡的水：前面的步驟再快，也只能照最慢那一關的速度離開。
noun · B2
The one slow step in a piece of work that holds up everything after it, so the whole job takes much longer than it should.
瓶頸