When I see my friend or if I see my friend? When I visited my brother or if I visited my brother? Is there always a difference between if and when, and if so, how do I know which to use? This is one of the most common question my students ask. In many languages, there is just one word for both, so it can be confusing. Here are some tips to help you remember when to use if or when.

Is it always true?

If you are describing something that is always true, you can use if or when and the meaning is the same. Both parts of the sentence should use the present simple. For example:

• When I’m tired, I go to bed. / If I’m tired, I go to bed.
• When they win, they’re happy. / If they win, they’re happy.
• When the price increases, we sell less. / If the price increases, we sell less.

Is it certain?

If something is definitely going to happen in the future, we use when. In these sentences, we’re sure that these things will happen and we’re describing what will happen in that situation.For example,

• When I see my friend, I’ll give her the information.
• When I give the presentation, I’ll speak loudly.
• When he goes to France, he’ll visit the Eiffel Tower.

If I’m not sure something will happen, we use if. All of these sentences talk about things that may or may not happen. For example:

• If I see my friend, I’ll ask her about her new job. (Maybe I will see her; maybe I won’t.)
• If I give the presentation, I’ll prepare well. (I don’t know if I will give the presentation yet.)
• If he goes to France, he’ll visit Nice. (He hasn’t decided yet if he’s going to France.)

If we swap if and will, the meaning changes:

• If I see my manager, I’ll ask her. (I don’t know if I’ll see her.)
• When I see my manager, I’ll ask her. (I know I’ll see her.)

Is it the past or just an idea?

If we are talking about something that really happened in the past, we use when.

• When I was at school, I liked art classes.
• When I lived in Scotland, we often went to the beach.
• When I visited my friend, we went to a great restaurant.

However, if we’re talking about unreal actions (in the past, present or future), we need if. These sentences describes ideas that didn’t or probably won’t happen. Here are some examples:

• If I won the lottery, I would buy a house.
• If I took a plane, I would get there quicker.
• If I had read the email, I wouldn’t have made the mistake.
• If I hadn’t been late, my boss would be angry.

Summary

So, to summarise, we use when to talk about something real in the past or certain in the future. We use if to talk about about things that are not certain or not real. We can use either if or when to talk about things that are always true.

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Do you have any more tips to help you remember when to use if or when? Do you have other questions about if sentences? Leave them in the comments below!