Recently, I posted about the difference between using “who” (referring to a person) or “that” (referring to an object, or a non-specific group). Here’s another minor glitch that shows up pretty often; although it does nothing to destroy the meaning of a sentence, it’s technically bound by rules, which can be of some importance if you’re trying to write correctly.

Did you see it? I just demonstrated both aspects of the issue in the same sentence. In the first part, the word “that” appears, starting a phrase that modified “glitch”; meanwhile, the last part of the sentence has the word “which” before the closing extended phrase.

Why is there a difference? It has mostly to do with the punctuation: in the first case, there’s no comma setting off the phrase, so “that” is the correct introductory-word; in the latter one, the comma allows “which” to take its rightful place. The reason is something called a “restrictive clause,” which is defined as something that cannot be taken out of the sentence without losing the meaning of said sentence.

I just showed both examples again (it’s hard to avoid sometimes):

The word “which” leads off a whole new clarification including the definition of the term, and could be dropped entirely and you’d still have a complete thought there (“The reason is something called a ‘restrictive clause’ …” is a complete sentence in itself.);

Meanwhile, the “that” in the extended sentence must be there in order for it all to make sense; if you cut off the end of the sentence from that point, you have, “The reason is something called a ‘restrictive clause,’ which is defined as something…” Without the “that” and its following words, the sentence just falls off a cliff, into the Gulch of Meaninglessness!

One more comparative example:

“Cars that use hybrid technology get better mileage.”

The “that phrase” tells you about specific types of cars, whereas:

“Cars, which move on the roadways, can be very dangerous at times.”

is stating a condition applicable to all cars, not just hybrids. (And yes, I know, some “cars” do not move on the roadways, but only sit in yards, propped up on blocks, or in repair-stations for most of their lives. Not the point here.)

I hope that made this at least a little clearer … If not, please do Comment and tell me how to say it better.