Photo: an example of proofreaders' marks for inserting a hyphen, an en dash, and an em dash. Most people use hyphens on a regular basis, but what about en dashes and em dashes? I didn't even know what they were until I went to university, and I wasn't familiar with how to use them until I took a grammar course for my Editing Certificate. So what are the differences between a hyphen, an en dash, and an em dash? Hyphen A hyphen is the shortest dash, and there is a key for it on