TWTS: If or whether you should use "if" or "whether"
If you worry about if or whether you should use “if” or “whether” in a construction just like this one, feel free to stop. Your bandwidth is valuable, and this isn’t the best use for it.
We didn't realize "if" and "whether" were causing some folks grief until our listener Dan Voetberg brought this concern to our attention.
“It seems to me that most people use ‘if’ when it seems to me that ‘whether’ would be more appropriate,” Voetberg said. “There’s a difference between the two in my mind, but I can’t put my finger on what it actually is.”
If you can’t put your finger on a difference between these two words either, that’s because there isn’t one. Not really, anyway.
However, we acknowledge that some of us grew up with the rule that you should use “whether” rather than “if” in the subordinating conjunction position. That includes Professor Anne Curzan.
“I had a very prescriptive mother who drilled these kinds of things into me, and there are still remnants of these rules in my head,” Curzan said. “I appreciated the chance to go look at this rule and discover that, as often happens, there is no good justification for this rule.”
There is one justification, but it’s tiny. You can decide for yourself if or whether it’s a good one.
The consensus in most usage guides is that “if” and “whether” are both standard in a construction like “I don't know if she's coming,” or “I don't know whether she's coming.” Both of these verbs have been used this way for more than a thousand years.
There are still some usage guides that say “whether” is preferred in formal contexts, but they don’t explain why. There's also the occasional case of ambiguity, such as this construction: “Let her know if she’s invited.”
This could mean that you should let her know whether she’s invited – maybe she is, maybe she isn’t. However, it could also mean that you should let her know, but only if she’s invited.
While it’s fair to say that “if” can occasionally be ambiguous, most of the time “whether” and “if” can be used interchangeably. If you’re wondering how we even got the idea that this wasn’t okay, listen to the audio above.