That vs. Which

Question

This question comes from graph theory (mathematics). Should I write, "A tree is a graph that has no cycles" or "A tree is a graph which has no cycles"?

Ruslana · Accepted Answer

Both sound okay to me.

Kooyeen · Answer

Hi, sorry, I feel I've got to hijack this thread at all costs!!!
No, seriously, I wanted to ask about this too. I'm sure that both "that" and "which" are ok (as Ruslana said), but I'd like ask this:

1) Is it true that "which" is not correct according to prescriptive grammar (since it's "restrictive") and it should be "that"?

2) Is it true that "which" sounds more formal than "that"? Does it sound formal?

3) If you answered yes to both of the above, then this is possibly the first case where what is "technically" incorrect is also more formal, right?

4) I believe native speakers are more likely to use "that" in everyday English. Is it true? Does "which" sound out of place in informal conversations, like "Hey dude, what ya doin? Did you see that awesome car which was parked in front of Bob&Brian's?"

Thanks in advance

CalifJim · Answer

1) Is it true that "which" is not correct according to prescriptive grammar (since it's "restrictive") and it should be "that"? In my opinion, no. It's only true in Microsoft Word and according to some people. I don't know where they got the idea, because I can't find a serious grammar book that says that only that is permissible in restrictive clauses.

2) Is it true that "which" sounds more formal than "that"? Does it sound formal? I think so. I tend to write which more, and say that more.

3) If you answered yes to both of the above, then this is possibly the first case where what is "technically" incorrect is also more formal, right? I didn't answer yes to both, so I don't have to answer this one!

4) I believe native speakers are more likely to use "that" in everyday English. Is it true? Same as Question 2. Yes. Does "which" sound out of place in informal conversations, like "Hey dude, what ya doin? Did you see that awesome car which was parked in front of Bob&Brian's?" This one would stand out somewhat for me, yes.

CJ

Kooyeen · Answer

Thank you! I don't know where I read that "which" is not correct in restrictive clauses, but I think I really read it somewhere. I'm sure I read it was a prescriptive rule, though. If I have tome, I'll try to find it.

PS: Hey, don't you think I'm starting to be interested in prescriptive grammar! It's just that I'm interested in this "which", which I don't like much, I have to say. I always tend to say "The car that was parked there", because I don't like to use "which" in restrictive clauses, like in "The car which was parked there". Actually, sometimes it's even kind of annoying, I could have listed in that thread about "the most annoying expressions". I know, I'm not normal, LOL

Anonymous · Answer

Thanks kindly for all of your replies. If I permute the sentence, it seems that "that" is needed.

1. A graph that has no cycles is called a tree. (This seems correct; I am restricting the scope of all possible graphs to those without cycles. Some graphs have cycles and some do not.)

2. A graph, which has no cycles, is called a tree. (This seems incorrect. The "which" indicates that "has no cycles" does not restrict the scope of graphs but only gives some additional information. This is not true of graphs.)

Does any of this matter??

I thought I learned from Strunk and White about the use of "that" versus "which" being related to whether the clause is restrictive or non-restrictive. Is this not always true?

Kooyeen · Answer

Hi, yeah, you are right:

A graph that has no cycles is called a tree. <--- if the graph has no cycles it's called a tree.

A graph, which has no cycles, is called a tree. <--- you are saying that all graphs have no cycles and are called trees, which isn't true.

By the way, I was wondering if your definition was correct. I thought that the graph probably had to be "connected" too, in order to be called a tree. But I wasn't sure, so I checked on Wikipedia, and it seems I was right. They say: "Any connected graph with no cycles is a tree".

MrPedantic · Answer

AnonymousI thought I learned from Strunk and White about the use of "that" versus "which" being related to whether the clause is restrictive or non-restrictive. Is this not always true?

Some style guides suggest that "that" presents restrictive (defining) information, while "which" presents non-restrictive (describing) information.

This is not true of ordinary usage, or in the works of "classic" authors, where both "which" and "that" may be found in restrictive clauses.

However, it is true that a non-restrictive that-clause is quite rare in current English, though common enough in earlier writers.

In your sentence, the comma makes the difference:

1. A graph that has no cycles is called a tree = A graph which has no cycles is called a tree.

— restrictive that/which.

2. A graph, (that)/which has no cycles, is called a tree.

— non-restrictive that/which.

MrP

Anonymous · Answer

Kooyeen,

You are correct. The graph should be connected as well. Good point.

Thanks for your help.

MrPedantic · Answer

Kooyeen the Anti-PrescriptivistHey, don't you think I'm starting to be interested in prescriptive grammar!

Kooyeen the Crypto-PrescriptivistIt's just that I'm interested in this "which", which I don't like much, I have to say. I always tend to say "The car that was parked there", because I don't like to use "which" in restrictive clauses, like in "The car which was parked there". Actually, sometimes it's even kind of annoying, I could have listed in that thread about "the most annoying expressions".

MrP

Kooyeen · Answer

Hey, MrP, what are you triyng to say? That I'm slowly becoming a prescriptivist? No way!!! LOL

Can't I NOT like something? I said I don't like it very much, I prefer "that", not that you must not use it. I know it's used and it's ok, it's just that I prefer not to use it that way... Maybe one day I'll change my mind. In English, I usually like what I'm used to and what I hear from certain kinds of people. So if I hear enough "witchs", one day I'll like them... but I hope I won't hear enough, LOL.

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