TIME CLAUSES

It is possible to use other words instead of if in first conditional sentences:

 

When:  When the “condition” will definitely happen in the future.

Look at the difference between these two sentences:

• If I see Sam, I’ll give him your message. (I’m not sure if I will see him or not)
• When I see Sam, I’ll give him your message. (I will definitely see Sam)

As soon as: To emphasize immediacy.

• My feet hurt! As soon as I get home, I’m going to take off these high heels.
• As soon as we have enough money saved, we’ll take a vacation to Costa Rica. We can’t wait!
• I’ll respond to your e-mail as soon as I can.

Unless: Substitute for “if not.”

• You won’t lose any weight unless you start eating healthier food.
  = You won’t lose any weight if you don’t start eating healthier food.
• I’m not going to dance unless somebody invites me.
  = I’m not going to dance if somebody doesn’t invite me.
• Unless there’s an emergency at work, I’ll be home on time.
  = If there’s not an emergency at work, I’ll be home on time.

- Exercise 1
- Exercise 2

Go to 'Grammar' to get the explanation as a document