Wednesday, November 18, 2009


One of the good things about my newish job at the London School of Economics is having to find stuff out. Interesting how often this will be answers to questions that have been hanging around in the back of my mind for some time.

Such as what's the difference between THAT and WHICH?

So here's my answer to the THAT/WHICH rule:

That is defining, and Which is not, so you would use That in a restrictive clause.

Er, yes. And...

I know, that helps me like a sack of potatoes too. How about if you use them in this way:

The essays that have to be in on Tuesday should be written in black ink


The essays, which have to be in on Tuesday, should be written in black ink.


The THAT example implies that ONLY the essays that have to be in on Tuesday should be written in black ink, and the WHICH example suggests ALL the essays need to be both in on Tuesday and written in black ink.

I've looked back through my old stuff and I've - mostly - used these two words correctly so the rule must have been implanted many years ago, but I've never actually unpacked it before.

Call me anal, but I LOVE all this.

Any grammar questions/rules/tips you want to throw at me before the students put me on the spot will be gratefully received.

Related posts:

How are your sentences?

Writing Do's and Don'ts

I'm a Winnie the Pooh Fellow


Caroline said...

I love it too and, just so you know,
being anal is the new black! x

SueG said...

How about my old fave, the semi-colon. I wrote about it here at

Feel free to use it. :-)

Sarah Salway said...

Brilliant, Sue; I'll use that (ps did you see what I did there?)
And yes, Caroline - we are not just today, we are tomorrow style-wise.

Kathryn's Daily Writing Workout said...

So glad you cleared up the that/which problem. I didn't know what the rule was and relied on whichever I thought sounded better. I get annoyed with myself every time it trips me up so it's nice to have a proper rule to follow. I like rules - thanks!

Pam said...

Thank you Sarah, brilliantly clear explanation. Lurking in my mind was that there needs to be a comma after which. Now I know why

Wendy said...

Fantastic - I've always wondered about this but have just gone on instict. Now I'll be checking every sentence I write.

Simon Suter said...

Could / Would

Would you please........ v.
Could you please.......