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The Meanings of Unless and If

In a lot of ways, it’s hard to truly know your own native language. Oh sure, you can follow the rules. But you follow them without thinking. Often, you don’t understand the rules consciously, and aren’t able to explain them to someone else who asks.

As an ESL teacher, sometimes knowing my own language can be as puzzling as my second language studies (I am currently studying Korean and Hmong). My students will often observe something unusual about my own language that I’ve never had to consciously think about. Recently, I was asked a very good—but very puzzling—question. A student wanted to know the difference between unless and if, and the rules for using those two words.

After spending a minute or two struggling to find an explanation, I told her I’d have to get back to her the next day. And then, with careful thought, I was able to consciously figure out the rules for these two words. I shared those rules with my students, and now I’m going to share them with you, my fellow Magooshers.

As you probably already know, “if” is conditional. It is used to describe a possible situation, and what would happen under the conditions of that situation.

“Unless” is also conditional, but it is effectively “if” with an extra exclusion or negative qualifier added. Unless basically means “except if” or “if… not”.

So you can make equivalent sentences with “if” and “unless.” Here are a few examples:


Example 1:

  • We will not go outside if it rains.
    • is the same as:
  • We will go outside except if it rains.
    • which is the same as:
  • We will go outside unless it rains.


Example 2:

The following sentences mean the same thing:

  • I will not travel to California this winter if I decide to go to Florida instead.
  • I will travel to California this winter except if I decide to go to Florida instead.
  • I will travel to California this winter unless I decide to go to Florida instead.


Notice that in shorter sentences (Example 1), if/not, except if, and unless are all equally good. But in longer sentences (Example 2), if/not sounds awkward, while except if is a little better. Unless is the best choice because it simplifies the wording, and makes longer sentences easier to follow.

And of course, you can’t replace unless with just if. It doesn’t make sense to say you’ll go to California if you go to Florida instead, and it would be strange to tell someone you’ll go outside if it rains. To be equal to unless, if needs other words added to it.

There are other pairs of sentences with if and unless that do not have the exact same meaning, but can complement each other. By this, I mean that an if sentence and an unless sentence can be used together to connect or ideas. In my next post on this subject, I’ll use some Magoosh Comics to show you how if and unless can appear right next to each other in the same conversation or piece of writing.

In the meantime, I highly recommend’s great video explanation of the grammar of “unless,” “if” and other similar words and phrases:

Click here for YouTube link, and here for non-YouTube link.

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