if, when, unless
We use (if/when/unless + present simple/will) + present simple to express general truths.
– When you heat water to 100°C, it boils/will boil.
We use (if/when/unless + present simple) + imperative to give a command.
– Stay here unless I tell you to leave.
We use (if/when/unless + present simple) + will/might/may/present continuous to express a condition referring to a possible present or future event
– Unless I hear from you, I‘ll go on my own.
– He might be prepared to do the job when he‘s finished his other work.
We use (if/unless + past simple/past continuous) + would/could/might/ought to to express a hypothetical condition referring to the present or future.
– If Anna went to college, she could study languages.
– I wouldn’t take my laptop unless I was planning to do some work.
We use (if/unless + past perfect) + would/could/might/ought to have to talk about a hypothetical condition in the past.
– Even if I‘d got the job, I probably wouldn’t have enjoyed it much.