只發生一次
這一家最貼近核心畫面，重點放在時間上：做過這一次，就沒有下一次了。
adjective · B2
Happening or done only one time, and not part of a regular series that repeats.
一次性的
核心畫面
Picture one thing lifted off the mould, and then the mould put away. There is that one piece, and there will be no second one. Every use of one-off grows out of that picture: the event held once, the offer nobody will repeat, the car built as a single example, and the person nobody else is quite like.
可以想成：一個東西從模子上被取下來，然後模子就收起來了。就只有那一個，不會再有第二個。one-off 的各種用法都像…更多收起
可以想成：一個東西從模子上被取下來，然後模子就收起來了。就只有那一個，不會再有第二個。one-off 的各種用法都像從這個畫面長出來——只辦一次的活動、不會再來的優惠、只做一台的車，還有那種「就只有這一個」的人。抓住這個畫面，形容詞和名詞的用法就會連成一條線。From the word’s history
Wiktionary derives it from one + off, and notes that it probably comes from foundry work, where moulds are expensive and normally reused. A one-off is the single piece taken off a mould that will not be used again. The same source says printmakers and sculptors have long used it for a unique print or casting, numbered 1/1.
維基詞典說 one-off 來自 one 加 off，可能出自鑄造工廠：模具很貴，通常會重複使用，而 one-off 指的是只從模子上取下那一個，不再做第二件。同一份資料也提到，版畫和雕塑界長期用 one-off 指「一版一件」，寫成 1/1。這條線索正好接上它今天的用法。
Wiktionary 'one-off'（封包 source_ref kaikki:3f6f69a190036ae4:917272632）
Two branches
獨一無二
如果只從模子取下一個，那自然沒有別的跟它一樣。重點就從「時間上只有一次」滑到「世界上只有一件」。
adjective · B2
Made or given specially as the only one of its kind, so nothing else is exactly the same.
獨一無二的