破折号有两种：（1）短破折号与（2）长破折号。许多人会混用这两种破折号。不过，它们各有不同的用途：短破折号（–）最常用来表示范围，而长破折号（—）则用来标示句子里的停顿。
短破折号用于数字之间表示起讫日期
短破折号可以用来表示起讫日期“从……到……”。该使用与同样表示起讫日期的“to”类似。
- Example
- Please solve problems 1-14 at the end of chapter 3.
- Example
- The school is accepting applications for the 2021-2022 academic year.
- Example
- She has a 12pm-12am shift.
要注意的重点是，短破折号不能取代“from…to…”里的 to。
- Incorrect
- She worked on her book from 2003-2013.
- Correct
- She worked on her book from 2003 to 2013.
长破折号用以表示句中停顿
长破折号用来表示思想上的中断或转移。这么说看起来不够明确，其实意思就是长破折号可以取代几种不同的标点符号：逗号、括号、分号和冒号。
使用长破折号可以取代逗号和括号。
- With Commas
- The evening sky, colored pink by the setting sun, was beautiful.
- With Parentheses
- The evening sky (colored pink by the setting sun) was beautiful.
- With Em Dashes
- The evening sky – colored pink by the setting sun — was beautiful.
长破折号可以取代分号。它不像分号那么正式，而且最常用来强调重点或语意的变化。
- With a Semicolon
- Mr. Mercer bought the book for fifteen thousand dollars; it was a first edition copy of Nabokov’s “Lolita.”
- With an Em Dash
- Mr. Mercer bought the book for fifteen thousand dollars — it was a first edition copy of Nabokov’s “Lolita.”
长破折号也可以取代冒号。它比冒号随意，强调性更重。
- With a Colon
- Ishiguro has finally released his new title: Klara and the Sun.
- With an Em Dash
- Ishiguro has finally released his new title — Klara and the Sun.
用短破折号取代长破折号
人们经常混用短破折号和长破折号，尤其是在非学术性的文章里。有趣的是，短破折号有时可以取代长破折号。但要注意的是，这种取代在英式英语中比美式英语更普遍。此外，切记要在同一篇文稿内让所有标点符号保持前后一致。
- Incorrect
- Ishiguro has finally released his new title – Klara and the Sun.
- Correct
- The evening sky – colored pink by the setting sun – was beautiful.