A Word, Please: Whether you use ‘if’ or ‘whether’ depends on the context

I don’t pay attention to the difference between “if” and “whether.” And that works out great. Just winging it, I have no trouble choosing “whether” in a sentence like “I don’t know whether to order the pasta or the pizza” and I have no trouble choosing “if” in a sentence like “If I order the pizza, I’ll have leftovers.”

In those examples, I don’t really have much choice. I’d never say, “I don’t know if to order the pasta or the pizza,” just as I’d never say, “Whether I order the pizza, I’ll have leftovers.

But not all whether/if choices are as clean. For instance, would you say, “I don’t know if it will rain” or “I don’t know whether it will rain”? Both work because both are correct. Yet some language cops have tried to take the simple logic of certain whether/if choices and make it into a rule governing every whether/if choice.

For example, a post some years ago on the Lit Reactor website argued: “‘Whether’ expresses a condition where there are two or more alternatives. ‘If’ expresses a condition where there are no alternatives.”

If this were true, which it’s not, it would mean that you could never say “I don’t know if it will rain” because there are two alternatives: It may or it may not rain.

This kind of arbitrary rule-making is nothing new. Back in the 1700s, language experts were arguing that you can’t use “if” after verbs like “question,” “see” or “know.” Different rule, same result: You can’t say, “I don’t know if it will rain.”

There was no basis for this prohibition in the 1700s, and there’s none now.

So why did anyone, at any point in history, waste even a minute trying to write a rule about “whether” and “if”? I’m not sure. It seems a lot of nonsensical grammar rules arose when people who were trying to explain some part of the language got carried away. They spotted some dynamic, like how you can’t say “I don’t know if to order the pasta” and tried to make a rule out of it, for example by declaring that you can’t use “if” after “know.” Soon, people are running around proclaiming that you can’t say, “I don’t know if it will rain.”

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But there are some real differences between “whether” and “if.” As Merriam-Webster’s Collegiate Dictionary explains it, “if” starts a subordinate clause in a conditional sentence. In other words, when one thing can happen on condition of the other, “if” works: If I order pizza, I’ll have leftovers. Here, I will only have leftovers on the condition that I order pizza. No pie, no leftovers.

But was there any chance you would use “whether” instead of “if” here? No. So you don’t need this rule.

As for “whether,” the dictionary tells us it is “a conjunction that usually starts a subordinate clause that expresses an indirect question involving two stated or implied possibilities or alternatives. And this is where the confusion starts: ‘if’ can also be used in this sense.” Maybe it will rain, maybe it won’t — either is possible. So “I don’t know whether it will rain” is correct here. But so is “I don’t know if it will rain.”

The closest thing to a pitfall with the word “whether” is the question of whether to add “or not”: I don’t know whether or not it will rain.

Some people say these extra words are unnecessary or even illogical. In most cases, they have a point. When conciseness counts, “or not” can usually be nixed. But if you feel like subjecting your reader to two extra syllables, you can. “Whether or not,” according to Merriam-Webster’s usage guide, is “perfectly good idiomatic English.”

June Casagrande is the author of “The Joy of Syntax: A Simple Guide to All the Grammar You Know You Should Know.” She can be reached at [email protected].