An SAT micro-topic explainer. Free to read — no account needed.
A non-essential phrase gives extra information that could be left out. To test one, read the sentence without the phrase. If it still makes sense and still points to the same thing, the phrase is non-essential.
A non-essential phrase must have the same kind of punctuation at both ends. You can use a comma before and a comma after, a dash before and a dash after, or a pair of parentheses. Mixing them — such as a dash on one end and a comma on the other — is incorrect.
Take the sentence: "The Nile, the longest river in Africa, flows north." Remove the phrase: "The Nile flows north," which still makes complete sense. So "the longest river in Africa" is non-essential, wrapped in a comma before and a comma after.
Compare this with an essential phrase, which the sentence needs and which takes no commas. In "The river that flows through Egypt is the Nile," the phrase "that flows through Egypt" is needed to say which river, so it gets no commas. The removal test tells them apart: if the sentence still points to the same thing without the phrase, the phrase is non-essential.
Worked examples
Is "my oldest friend" non-essential in this sentence: "Priya, my oldest friend, is moving to Canada"? Remove the phrase: "Priya is moving to Canada," which still makes sense and still names Priya. So "my oldest friend" is non-essential and takes a comma before and a comma after.
How should the phrase "a huge fan of jazz" be punctuated in "My uncle, a huge fan of jazz, plays the saxophone"? Remove the phrase: "My uncle plays the saxophone," which still makes sense, so the phrase is non-essential. Set it off with matching marks on both ends — a comma before and after, or a dash before and after — but not one of each.
Which phrase is non-essential: "which took years to finish" in "The painting, which took years to finish, hangs in the hall," or "that won the prize" in "The painting that won the prize hangs in the hall"? Remove "which took years to finish": "The painting hangs in the hall" still makes sense, so that phrase is non-essential and takes commas. But "that won the prize" is needed to say which painting, so it is essential and takes no commas.
Is this one of the topics costing you points?
Take the free 10-question diagnostic for a predicted SAT score and a breakdown of which domains are costing you points.