The most common coordinating conjunctions are and, but and or. It might be helpful to explore the uses of these tiny conjunctions.
And has several uses.
1) To suggest that one idea is chronologically sequential to another:
- I lay down and went straight to sleep.
2) To suggest that one idea is the result of another:
- She worked hard and won the first prize.
- We heard the weather forecast and promptly cancelled the trip.
3) To suggest that one idea is in contrast to another. In this usage, and is frequently replaced by but.
- She is a doctor and I am just a road-sweeper.
4) To express a condition. It is often possible to express the same idea using if.
- Do that again and I will hit you. (= If you do that again I will hit you.)
- Use your credit cards frequently and you will soon find yourself in debt. (= If you use your credit cards frequently, you will soon find yourself in debt.)
5) To suggest a kind of ‘comment’ on the first clause:
- It didn’t take him long to get addicted to gambling – and that surprised no one.
But is used to suggest a contrast that is unexpected in light of the idea expressed by the first clause.
- His rope was thin but it was strong.
- He is fat but he runs fast.
- She is poor but she is happy.
But can mean except after words like all, none, every, any, no, everything, everybody, nothing, nobody etc.
- He eats nothing but hamburgers. (= He eats nothing except hamburgers.)
- I have cleaned all rooms but one.
- Everybody came but Peter.
Or is used to suggest that only one possibility can be realized.
- You can have tea or coffee.
- He offered her a bun or a sandwich.
- You can work hard for this exam or you can fail.
- Is it green or blue?
- He is not sane or brilliant.
Or can be used to introduce a word that explains or means the same as another.
- He carries a revolver, or pistol, in his belt.