Mekita Rivas, SNR communications associate, publishes a biweekly feature called "Grammar Guru."
Every other week, the Grammar Guru will share writing tips to help make your work as polished as possible. Some of these tips may address common spelling errors, while others will examine the many nuances of the English language.
Grammar Guru Tip #14
Knowing whether to use "which" or "that" is one of the most common sources of confusion in the English language. "That" is a restrictive pronoun, meaning it's vital to the noun to which it's referring.
Example:
I don't like to drink coffee that I didn't brew myself.
Here, I'm referring to all coffee that can be brewed, but I only drink coffee that I brew. "That" is used to restrict.
"Which" introduces a relative clause that may or may not be essential to the sentence.
Example:
I recommend you brew coffee at home, which is cheaper than going to a coffee shop every day.
Here, "which" qualifies my recommendation, but the clause it introduces is not essential for the sentence to be grammatically correct.
Pro tip: "Which" is almost always preceded by a comma; "that" is rarely preceded – or followed – by a comma.
Example:
The computer, which has a virus, is mine.
The computer that has a virus is mine.
Need some grammar guidance? The UNL Style Guide (http://unlcms.unl.edu/ucomm/styleguide/) is a great resource for all university employees. If you have writing questions that the style guide doesn't answer, feel free to email the Grammar Guru at mrivas@unl.edu.