Lesson
When we want to talk about things that are always or generally true, we can use:
If/When/Unless plus a present form PLUS present simple or imperative
- If you press this button, you get black coffee.
- When you fly budget airline, you don't expect to get anything to eat.
- Unless you need a lot of leg-room, don't pay the extra for first class.
Notice that we are talking about something which is generally true, not a specific event.
In the condition clause, there can be a variety of present forms. In the result clause, there can only be the present simple or imperative.
- If you visit Barcelona, look out for the spectacular architecture.
- If unemployment is rising, people tend to stay in their present jobs.
- If you've finished everything, go home.
- When you go to Barbados, take plenty of sun cream.
- When I'm working, please be quiet.
- When I've written a new article, I run it through my spell-checker.
Notice that 'unless' means the same as 'if not'.
- Unless he asks you to continue, stop all work on the project.
- Unless interest rates are rising, it's not a good investment.
- Unless you've been to Tokyo yourself, you don't really understand how fantastic it is.