Colons (:) have three uses.
They are used to introduce a list:
- We can see many things in the sky at night: the moon, the stars, the planets, comets and even planes.
- Please check the following:
1. the bedding
2. the towels
3. the kitchen utensils
4. the pots and pans
They are used to introduce a single item, when you want to emphasise that item:
- There is one thing that he will not accept: stupidity.
- We forgot to ask the most important question: who is buying lunch?
They are used to show the time:
- The meeting starts at 8:15pm.
- 09:00
- 21:00