OH, GREAT–the day I post a GQ question I really need an answer to . . .
Lemme try here: can anyone tell me in words a 5-year-old could understand the difference between “which” and “that?” As in “It was the role which won her an Oscar” and “It was the role that won her an Oscar?”
Please don’t tell me to read the Chicago Manual of Style, I couldn’t make head or tail of it.
I answered this in your other thread but obviously you can’t read it there, so…
Use “that” if you are specifying one of a number of things: “the lawnmower that is broken is in the garage.” (tells which one)
Use “which” if you are adding information about a particular one: “The lawnmower, which is broken, is in the garage.” (adds a fact about the only lawnmower in question)
In general, a clause that uses “which” will also be set off with commas as above.