To double-book is to promise the same seat, room, or time to more than one person — usually by mistake. A theatre, an airline, a hotel, or a busy clinic might do this when two people book the same slot, or when a computer list and a paper list get out of step. The second person to arrive is the one who finds out. You can also double-book yourself: you say yes to two meetings at the same hour.

To double-book is是 the same seat, room, or time把同一個座位、同一間房或同一個時段 to promise答應 to more than one person給超過一個人——usually by mistake通常是不小心的。A theatre, an airline, a hotel, or a busy clinic劇院、航空公司、旅館或忙碌的診所 might do this都可能發生這種事，when two people book the same slot當兩個人訂了同一個時段，or when a computer list and a paper list或當電腦名單和紙本名單 get out of step對不上的時候。The second person to arrive後到的那個人，is the one who finds out就是發現真相的那個。You你 also也 can double-book yourself可以重複預訂你自己：you你 to two meetings at the same hour對同一個小時的兩場會議 say yes都說好。

Though actually this is not the same as “overbook”. Some companies overbook on purpose: they sell more tickets than seats, betting that a few people will not come. Double-book is the accident of giving the same thing twice; overbook can be the plan.

Though actually不過其實，this這 as “overbook”跟 “overbook” is not the same不一樣。Some companies有些公司 on purpose是故意 overbook超賣的：they他們 than seats比座位 sell more tickets賣出更多票，betting賭 that a few people will not come會有幾個人不來。Double-book is是 giving the same thing twice同一樣東西給了兩次 the accident of的意外；overbook can be則可以是 the plan計畫好的。

The word belongs to everyday service talk — desks, phones, diaries — not to formal law language.

The word這個詞 belongs to屬於 everyday service talk日常的服務場合用語——desks櫃檯、phones電話、diaries行事曆——not to formal law language而不屬於正式的法律語言。