In her latest On Language column — er, uh, in her The Word column, in which she actually cites William Safire as a source — Globe language scribe Jan Freeman posed an interesting question. I tried responding to her directly, but the e-mail bounced twice, so I’m giving up and just posting it here. First, Jan:

IF, WHETHER, OR NOT? Grammar Girl, the popular usage podcaster, offers “quick and dirty” usage advice, most of it reliably mainstream. But her recent treatment of whether and if has me stumped.

In my experience, the only real problem in the “whether/if” department is that overzealous editors sometimes delete an obligatory “or not.” But Grammar Girl sees another potential problem. She claims these sentences have different meanings:

Squiggly didn’t know whether Aardvark would arrive on Friday or Saturday.

Squiggly didn’t know if Aardvark would arrive on Friday or Saturday.

I don’t see it, but I’d like to know if readers do (without the aid of Grammar Girl); please send explanations (or exclamations!) to freeman@globe.com.

To which I say: I’ve never heard of Grammar Girl, but I’m semi-siding with her on this one.

Squiggly didn’t know whether Aardvark would arrive on Friday or Saturday. This seems to mean that Aardvark will arrive on either Friday or Saturday. The “whether” implies that these are the only two possible outcomes, and that one will come true.

Squiggly didn’t know if Aardvark would arrive on Friday or Saturday. This seems to mean that Aardvark may arrive on Friday or Saturday, or maybe Sunday, or Monday. The “if” suggests that “Friday or Saturday” is one, joint outcome — an arrival on one of these days — but in the context of the sentence, it’s unclear if Aardvark will arrive on one of those days. It’s equal to saying, “Squiggly didn’t know if Aardvark will arrive.”

This is tricky, though, because I don’t think the whether/if split in meaning would be as clear if the sentence included only one potential outcome. For example:

Squiggly didn’t know whether Aardvark would arrive.
Squiggly didn’t know if Aardvark would arrive.

Those two mean the same thing, because there’s only one outcome presented, and the suggestion from both “whether” and “if” is that this one outcome may not be achieved. Which, I suppose, means I don’t know whether or if I’m right at all.