Which Hunt

Der Liebeszauber

I'm never sure whether to use which or that.
It's almost Halloween, so d'you fancy coming on a which hunt with me?

It's actually rather complicated (to my inferior mind), and I'll try to simplify as much as is humanly possible.
So here's the deal:

The problem I have with which and that comes from my use of relative pronouns.

Relative pronouns refer back to people or things previously mentioned:

People who wee should use the toilet.

Okay, fine so far. If we're discussing people in this manner, we use who.
Who is the relative pronoun: it refers back to people.

But what about non-people things?

We use THAT to introduce an ESSENTIAL clause.
We use WHICH to introduce a NON-ESSENTIAL clause.

Sorry? What is a clause?
Well, a clause is a group of words containing a subject and a verb.

And essential and non-essential clauses?
There are several ways of identifying such clauses:

The simplest test is this:
Remember how we can partition off non-essential stuff with commas?

The bathroom, which had blue tiles, was down the hall.

Yes, it's that simple! By placing a chunk of your sentence between commas, that chunk is non-essential: you could take it out and the sentence would still work fine. Take a look:

The bathroom was down the hall.

See, it still holds water (pun intended)!
In that example, 'which had blue tiles' is called an adjective clause. Like many adjectives, we can lose them without harming the reader's understanding. Non-essential, see!

* So, if we place a clause between commas, it is NON-ESSENTIAL and we use WHICH.

Now, what if there were loads of bathrooms in the house?

Imagine that:
the bathroom with blue tiles is down the hall;
the bathroom with red tiles is upstairs;
the bathroom with yellow tiles is in the cellar.
Sure is a queer house!

Ah, well now the adjectives are important aren't they!
The adjectives are now essential because they alter the reader's understanding: I could send the reader down the hall to the bathroom with blue tiles, or maybe upstairs to the bathroom with red tiles.
What do we do with essential clauses? We forgo the commas and we use THAT:

The bathroom that had blue tiles was down the hall.

The bathroom that had red tiles was upstairs.

* If we alter the meaning with a clause, the clause is ESSENTIAL and we use THAT.

And finally:
If we use this, that, these, or those to introduce an essential clause, we always introduce the next clause with which.
So, if we open with THAT, we move on to WHICH.

That is a problem which has now been resolved!

Same goes for THIS, THESE and THOSE.


Here's a basic summary:

*People use WHO.
*Essential things (stuff that is required for the sentence to make accurate sense) use THAT.
*Non-essential things (stuff that could be removed, or sits between commas) use WHICH.
*When introducing with THIS, THAT, THESE or THOSE, we move on to WHICH.


Now take this test.
Forget what you thought you knew, stick with what I've just explained, and you'll score full marks.


Feeling brave?
Then take this grammar test.
I scored 40 out of 50, WHICH means THAT I will continue to learn and to blog!

Here's why I have devoted my Saturday morning to this research:

As it [the tunnel] twisted off into the musty distance, stone pillars tapered into towering arches high above which contorted into wide and improbable vaulted ceilings.

The relative pronoun refers back to the towering arches. It leads to information that is non-essential: the vaulted ceilings apply to all of the towering arches and could easily be removed without harming the reader's understanding, just like the bathroom which had blue tiles. Phew.

There are detailed rules here:
Get it Write
The Blue Book of Grammar and Punctuation