What’s the Difference Between If and Whether?

I’m back to the subject of conjunctions (you know…those things that link parts of sentences together). This time, rather than focusing on conjunctions and punctuation, this post is about the difference between two similar conjunctions: if and whether. As a disclaimer, these tips are for formal, technical writing—not everyday speech or fiction. So don’t beat yourself up trying to figure out when to use “whether” when you speak.

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Now that I’ve gotten that out of the way, what’s the difference between if and whether? If means “in the event that” or “on the assumption that.” It’s conditional, meaning some condition must be met for something else to happen (If this happens, then this next thing will happen …or this will happen if something else happens first).

I will be relieved if I pass my CEN exam this week.

This means I’ll be relieved on the condition that I pass my exam.

If the patient is pregnant, it is recommended to wait until the postpartum period to treat her for CIN grade 3.

A patient being pregnant means it’s recommended to wait to treat her for CIN grade 3.

Here’s a similar conditional sentence:

In cirrhosis, the appearance of the ascitic fluid is typically clear yellow, but it can be milky if chylous ascites is present.

The presence of chylous ascites means the ascitic fluid may be milky.

Whether, on the other hand, indicates an alternative:

I’m trying to decide whether to start my PANRE review now or next month.

There are two alternatives here: (1) starting my PANRE review now or (2) starting it next month.

A 40-year-old woman presents to your office to discuss whether she should begin yearly screening mammography.

This sentence doesn’t state both alternatives. In this case, they’re implied as (1) she should begin yearly mammograms and (2) she should not begin yearly mammograms.

Try out some examples:

More than one treatment with percutaneous ethanol injection is often required, particularly [whether/if] a patient has multilocular or sizable cysts.

Is this sentence conditional (one thing must happen for something else to happen) or is it discussing alternatives? If you said conditional, you’re correct! More than one treatment with percutaneous ethanol injection is often required, especially on the condition of multilocular or sizable cysts.

He is able to tell [whether/if] his feet are flexed or extended.

This time we only care about two alternative options: flexed or extended. Whether is correct!

As I mentioned earlier, we’re focused on technical writing here. If you said the previous example out loud, you might use if instead of whether. And surprise…everyone would know what you mean, very few people would faint over it, and no one should notice or care because it’s common wording. But because we’re discussing medical writing, we want to be a bit more formal, clear, and grammatically correct. 

Last example:

I’m committed to doing 20 board review questions tomorrow, [whether/if] it’s sunny or raining!

This sentence has a different meaning when we use if or whether. Let’s break it down:

“…whether it’s sunny or raining” means I’m going to study no matter what—rain or shine.

“…if it’s sunny or raining” means I’m only going to study on two conditions: either sun or rain. A cloudy, rainless day must give you a free pass. (Tricky conditional sentence there—you should do yourself the favor and study anyway.)

English is full of these words that have similar meanings but different usages. And it has plenty of words that we use differently in speech versus writing! But if you’re creating technical, formal pieces, remember to figure out whether your sentence is conditional or discussing alternatives if you want to keep things clear for your readers. Happy writing!