“This is my en rule. There are many like it, but this one is mine.
My en rule is my best friend. It is my life. I must master it as I must master my life.” (A minor bastardization of the Rifleman’s Creed.)
Em rules and en rules. This is advanced grammar-pedant knowledge and you can be certain to impress friends and pedants if you casually whip out this puffy point of punctuation knowledge. Both look like dashes but the em rule is a longer dash than the en rule: — vs –
Think of the en rule as a pistol and the em rule as a shotgun. Both are used—like commas and brackets—to denote a break in a sentence or to set off parenthetical statements. However, only en rules can be used with date spans e.g. The Merkin Revolution (1812–1813) was a period of great social unrest.