SAT Grammar 2: Commas and Essential vs. Non-Essential InformationSAT Grammar 2: Commas and Essential vs. Non-Essential Information

S A T R E A D I N G A N D W R I T I N G · GRAMMAR

Commas and Essential vs. Non-Essential

Information

SAT Grammar Guide 2

Goal: Use commas correctly and tell essential information (no commas) from non-essential information (set off with punctuation).

Original study notes on standard SAT grammar and punctuation rules, with original examples. Not copied from any prep book.

Big Picture

Commas are tested for what they do, not how many there are. Most comma questions reduce to four jobs: lists, introductions, joining sentences with a conjunction, and setting off extra information. When Commas Are Required

Series of three or more: "She packed a tent, a stove, and a map."

Coordinate adjectives that could be joined by "and" or swapped: "a quiet, patient teacher." No comma if they cannot be swapped: "a small wooden boat."

After an introductory word, phrase, or clause: "After the storm passed, the crew went outside." Before FANBOYS joining two ICs: "The lab was closed, but the library was open."

Non-Essential (Extra) Information

If you can remove a phrase and the sentence still makes sense and keeps its meaning, the phrase is non-essential and must be set off by a matched pair of commas, dashes, or parentheses.

"Marie Curie, a physicist and chemist, won two Nobel Prizes."

Pair rule: use both or neither. A single comma between a subject and its extra information is an error. Essential information is needed to identify who or what is meant, so it takes no commas: "The student who finished first received a prize."

Which vs. that: "which" usually starts non-essential information (with commas); "that" starts essential information (no commas). "Who" works for either.

Appositives: a name after a one-of-a-kind noun is non-essential ("My sister, Dana, lives in Austin" if you have one sister). If the noun is not unique, the name is essential ("My friend Dana lives in Austin"). Common Comma Errors

Error Wrong Right

Between subject and verb The tallest tree in the park, fell. The tallest tree in the park fell. Between verb and object She enjoys, reading history. She enjoys reading history.

After "that" He said that, the plan worked. He said that the plan worked.

Between two verbs sharing one subject The pilot checked the gauges, and

landed.

The pilot checked the gauges and landed.

One comma around extra information The mayor, who was elected in May

spoke.

The mayor, who was elected in May,

spoke.

Before a dependent clause that follows an

IC

She left early, because she was tired. She left early because she was tired.

Key Terms

Term / Actor What it is and why it matters

Non-essential clause Extra information, set off with a pair of commas, dashes, or parentheses. Essential clause Information needed to identify the noun; no commas.

Appositive A noun phrase that renames the noun beside it.

Coordinate adjectives Adjectives of equal rank, separated by a comma.

Introductory element Opening word, phrase, or clause followed by a comma.

Making This Essay-Ready

Test: Remove the phrase. If the sentence still identifies the same person or thing, it is extra and needs a pair. Trap: Matching punctuation: a comma on one side and a dash on the other is wrong.

SAT Grammar Guide 2 · Original SAT grammar study notes