Whether they realize it or not, most people have some sort of list of traits that they consider essential in a romantic partner. ”These things I will not live without in a relationship!” they cry, pointing to items 7 (“Likes shellfish, but doesn’t love it more than regular food, like bird meat”) and 44 (“Keeps the toilet seat weighted down with tubes of toothpaste squeezed from the middle”).
Then time goes on. The emails from dating sites like e-Melodies and MyFriendSignedMeUpForThisAccountIsn’tItFunnyIThinkI’llJustKeepItJustBecauseTheyDidThatFunnyJokeRememberItWas MyCrazyFriendWhoDidThisNotMeItWasn’tMe.com slow down. Desperation sets in. And suddenly, what is “essential” in a relationship changes. Items are mentally crossed off the “list” until it’s at the bare minimum:
2. Doesn’t spell “congratulations” with a d.
(A girl’s gotta have some standards.)
This idea of what is essential and what is not is key to understanding today’s topic: when do you use that in a sentence and when do you use which?
Here’s the short answer: use that to introduce an essential clause and use which to introduce a non-essential clause.
Here’s a longer explanation: an essential clause is a part of a sentence that needs to be there in order for a sentence to make sense or fulfill its purpose.
Example: Books that include their own title in the climax annoy me.
In this sentence, “that include their own title in the climax” is an essential clause because the sentence doesn’t fulfill its purpose without it. If I took that part it out, the sentence would just say, “Books annoy me.” This is obvious not the point the sentence is trying to make. Therefore, the clause is essential.
Another Example: A book series that does this is Twilight, by Stephenie Meyer. Don’t ask me how I know.
“That does this” is an essential clause because it is specifying what series I’m talking about; the entire meaning is lost if it is taken from the sentence.
A non-essential clause is just the opposite: it is a clause that can be lifted out of the sentence without having any effect on the grammar or meaning.
Example: This duck, which I have not named yet, looks like he might respond to the name “Puck.” Probably because it rhymes with “duck.”
“Which I have not named yet” is a non-essential clause. Take it out of the sentence, and the sentence still makes complete sense. Therefore: non-essential. It doesn’t need to be there for the sentence to function–it’s just an extra bit of information.
That’s all that you need to ask yourself when deciding if you should start a clause with that or which. Another tip/clue: which clauses are set apart with commas (as you can see in the example). Think of these commas as hooks with which you can lift the clause out of the sentence.
And who knows? Maybe while fishing in these sentences you’ll hook yourself a nice, handsome clause you can take home at Christmas and introduce to your parents. Just as long as that clause doesn’t include the word “congradulations.” That’s just not how that word is spelled.