The dash mark (-) is a punctuation mark with a horizontal line that shows a pause or break in meaning, or that represents missing words or letters.

Dashes are often used informally instead of commas, colons and brackets. A dash may or may not have a space on either side of it.

Rule 1.Use a dash to show a pause or break in meaning in the middle of a sentence.

• My brothers—Richard and John—are visiting Hanoi.
• In the 15th century—when of course nobody had electricity—water was often pumped by hand.

Rule 2. Use a dash to show an afterthought.

• I attached the photo to my email—at least I hope I did!

Rule 3. Use a dash like a colon to introduce a list.

• There are three places I'll never forget—Paris, Bangkok and Hanoi.
• Don't forget to buy some food—eggs, bread, tuna and cheese.

Rule 4. Use a dash to show that letters or words are missing.

• They are really f––––d up.
• I will look ––––– the children.