Picking up where we left off last time, let’s talk about the expendable which and the necessary that.
KNOWING WHEN TO USE WHICH AND THAT
Expendable which
The which is expendable because if you were to leave it off the sentence, the OG (original) meaning of the sentence stays the same.
For example, “Bob lost the softball game, which is bad news.”
The point is that Bob lost the softball game. The “which is bad news” part is just an aside.
Grammar Girl’s quick and dirty tip: "You can throw out the 'whiches,' and no harm will be done."
You use which in nonrestrictive clauses, and if you eliminate that clause, the meaning of the sentence remains the same.
Necessary that
However, if throwing out the clause would change the meaning of the sentence, it’s a “that” that should be used.
The example Grammar Girl gives is: “Cars that have hybrid technology get great gas mileage.”
If you took out the “that have hybrid technology,” you’d be saying that cars get great gas mileage.
Or for instance: “Leaves that are green contain chlorophyll.”
Take out the that, and you’re saying “Leaves contain chlorophyll.”
Both have different meanings without the restrictive clause. (Also note: restrictive clauses aren’t set off by commas. Only non-restrictive clauses take commas.)
So just remember, if you could throw out the clause without changing the meaning of the sentence, it’s a “which” clause. If not, go with that, and leave out the commas.
KNOWING WHEN TO USE WHICH AND THAT
Expendable which
The which is expendable because if you were to leave it off the sentence, the OG (original) meaning of the sentence stays the same.
For example, “Bob lost the softball game, which is bad news.”
The point is that Bob lost the softball game. The “which is bad news” part is just an aside.
Grammar Girl’s quick and dirty tip: "You can throw out the 'whiches,' and no harm will be done."
You use which in nonrestrictive clauses, and if you eliminate that clause, the meaning of the sentence remains the same.
Necessary that
However, if throwing out the clause would change the meaning of the sentence, it’s a “that” that should be used.
The example Grammar Girl gives is: “Cars that have hybrid technology get great gas mileage.”
If you took out the “that have hybrid technology,” you’d be saying that cars get great gas mileage.
Or for instance: “Leaves that are green contain chlorophyll.”
Take out the that, and you’re saying “Leaves contain chlorophyll.”
Both have different meanings without the restrictive clause. (Also note: restrictive clauses aren’t set off by commas. Only non-restrictive clauses take commas.)
So just remember, if you could throw out the clause without changing the meaning of the sentence, it’s a “which” clause. If not, go with that, and leave out the commas.