And, But, Or, So, Because

These five short words join words and sentences. Each one has its own job:

• and adds something: My mum and dad are at work.
• but shows a contrast or a surprise: It's cheap, but it's good.
• or offers a choice: Tea or coffee? After an order it means "otherwise": Hurry, or we'll be late.
• so gives the result: It was dark, so I turned on the light.
• because gives the reason: I'm hungry because I missed lunch.

So and because point in opposite directions: the reason comes after because, the result comes after so. Use a comma before but and so when they join two sentences, but usually no comma before because.