Commas To Set Off Quotes & Sayings

A dependent clause (a sentence fragment set off by commas, dontcha know) helps you explore your story by moving you deeper into the sentence. It allows you to stop and think harder about what you've already written. Often the story you're looking for is inside the sentence. The dependent clause helps you uncover it. — Janet Fitch

Using which instead of that. That introduces essential clauses while which introduces nonessential clauses. Consider the sentence "Tools that have sharp edges can cause nasty cuts." If you remove the words "that have sharp edges," the sentence loses much of its meaning. The clause is essential. Now consider "Roses, which come in many colors, have thorns on their stems." You can remove "which come in many colors" and the meaning of the rest of the sentence is intact. The clause is not essential. Another way to remember: If the clause obviously needs to be set off by commas, use which. — Charles Murray