Common grammar mistakes - Which or that?

Which is correct?

The new company camcorders, _______ are smaller and take better video, cost half as much as the camcorders we already had.
a. which
b. that

Answer:a

This is a tricky one because you have to look at the meaning of the sentence. In the sentence above, the fact that the new cameras are smaller and take better video is not essential to the meaning of the sentence.  ( The essential fact is that they cost half as much.) Use which.

In a statement, that introduces essential information in what is called a restrictive clause. Which introduces extra information in what’s called a nonrestrictive clause.

Here’s an example of how choosing which or that can change the meaning of the sentence.

• The computers are new.
• The computers, which have 2 gigs of RAM, are new. (you are providing extra information about the new computers)
• The computers that have 2 gigs of RAM are new. (you are saying that only the computers with 2 gigs of RAM are new — the others are old)

Need an easy way to remember? Use which if you’re providing nonessential information.