Commas and Extra Information

American Diploma › Digital SAT Reading and Writing — Complete Course

What this question type tests

Comma questions are part of the Boundaries skill in the Standard English Conventions domain (about 26% of the scored Reading and Writing questions, 11–15 questions in total). The College Board describes this skill as punctuation inside sentences: separating list items, setting off supplements such as appositives and parenthetical phrases, and knowing when no punctuation is needed — for example, never between a subject and its verb.

The format is always the same: one short passage (25–150 words) with a blank and the question “Which choice completes the text so that it conforms to the conventions of Standard English?” The four choices usually contain the same words with commas, dashes or brackets in different places — or with no punctuation at all. Very often the correct answer is the one with less punctuation.

To answer these questions you need two skills: (1) deciding whether a piece of information is essential or extra, and (2) knowing the places where a comma is never allowed.

Rule 1: Essential vs non-essential information — the removal test

Non-essential (extra) information adds detail, but the sentence still makes sense and keeps its main meaning without it. It is set off with punctuation. Essential information tells us *which one* we are talking about; without it the meaning changes or becomes unclear. Essential information takes no punctuation.

The removal test: cover the words you think are extra. Read what is left.

1. If the sentence is still complete and still says the same main thing → the words are extra → put them between a matching pair of punctuation marks.
2. If the sentence breaks, or the meaning changes → the words are essential → no commas.

Rule 2: Matching pairs — comma…comma, dash…dash, bracket…bracket

Extra information in the middle of a sentence needs punctuation on both sides, and the two marks must match. You may choose commas, dashes or brackets, but you cannot open with one and close with another.

• ✓ The festival, held every spring, attracts thousands of visitors.
• ✓ The festival—held every spring—attracts thousands of visitors.
• ✓ The festival (held every spring) attracts thousands of visitors.
• ✗ The festival, held every spring—attracts thousands of visitors. (comma … dash)
• ✗ The festival—held every spring, attracts thousands of visitors. (dash … comma)
• ✗ The festival, held every spring attracts thousands of visitors. (pair not closed — now a comma separates the subject from the verb)

If the extra information comes at the end of the sentence, you need only the opening mark; the period closes it: “The prize went to Hana Fouad, a young engineer from Aswan.”

Rule 3: Appositives (a noun that renames another noun)

An appositive is a noun phrase that renames the noun next to it: “Naguib Mahfouz, a Nobel Prize winner, was born in Cairo.” Most appositives are extra information and take a pair of commas (or dashes).

• ✓ Aswan, a city on the Nile, is famous for its granite.
• ✓ The class read Animal Farm, a short novel by George Orwell.
• ✗ Aswan a city on the Nile, is famous for its granite. (opening comma missing)

Rule 4: Names and titles — “the biologist Maria Lopez” vs “the biologist, Maria Lopez,”

This is one of the most tested comma rules on the SAT, and many students get it wrong because their ear wants a pause. Learn it as a set of patterns:

Why? In “the biologist Maria Lopez,” the name identifies which biologist out of many — remove it and you only have “the biologist,” which is unclear. In “the team's only biologist, Maria Lopez,” we already know exactly who it is, so the name is extra.

Rule 5: Relative clauses — which, that, who

• ✗ The line, that runs to Helwan, is the oldest. (“that” never takes commas)
• ✗ The Cairo Metro which opened in 1987, carries millions of passengers. (pair not opened)
• ✓ After a named person, a who-clause is usually extra: “Dr. Nadia Samir, who leads the project, …”

Rule 6: Introductory words, phrases and clauses

Put a comma after an introductory element that comes before the main clause: a dependent clause, a long phrase, or a transition word.

• ✓ Because the road was flooded, the bus took a different route.
• ✓ After three years of careful restoration work, the old station reopened.
• ✓ However, the results were not final.
• ✓ Opened in 1869, the Suez Canal shortened the trip from Europe to Asia.
• ✗ Because the road was flooded; the bus took a different route. (a semicolon needs a complete sentence on both sides)

Rule 7: Items in a list (the serial comma)

Separate three or more items with commas. The comma before the final “and” or “or” is called the serial comma (or Oxford comma). Using it is always safe, and it often prevents confusion.

• ✓ The kit contains a compass, a flashlight, and a first-aid manual.
• ✗ The kit contains a compass a flashlight, and a first-aid manual. (missing comma between the first two items)
• ✗ The kit contains, a compass, a flashlight, and a first-aid manual. (no comma between the verb and its object — see below)
• ✓ Two items only: “a compass and a flashlight” — no comma.

When the list items themselves contain commas, the SAT may use semicolons between items — that special rule is taught on the next page (Colons, Dashes and Semicolons).

When NOT to use a comma — the big list

On the SAT, an unnecessary comma is wrong, not “a matter of style.” Many questions are built so that three choices add a comma in a forbidden place and only one choice has no punctuation. Learn these no-comma zones:

Worked examples

Worked example 1 — matching pair

Text: Many visitors to Egypt never travel west of the Nile Valley, but those who do are rarely disappointed. The Siwa Oasis—famous for its dates, olives, and the ruins of an ancient oracle temple ______ lies about 50 kilometers from the Libyan border.

Which choice completes the text so that it conforms to the conventions of Standard English?

• A) temple,
• B) temple—
• C) temple
• D) temple;

Answer: B

• A) ✗ Wrong: The extra information opened with a dash after “Oasis,” so it must close with a dash, not a comma. Comma … dash is a mismatched pair.
• B) ✓ Correct: A dash closes the dash that opened the extra information. Remove it and the skeleton is complete: “The Siwa Oasis lies about 50 kilometers from the Libyan border.”
• C) ✗ Wrong: With no closing mark, the reader cannot see where the extra information ends.
• D) ✗ Wrong: A semicolon needs a complete sentence before it; “The Siwa Oasis—famous for …” is not one.

Worked example 2 — subject and verb

Text: Archaeologists have long debated when people in Egypt first began to farm. The researchers who studied the ancient grain samples from the Fayoum ______ that farming in the region began earlier than many experts had expected.

Which choice completes the text so that it conforms to the conventions of Standard English?

• A) Fayoum, concluded
• B) Fayoum concluded
• C) Fayoum, concluded,
• D) Fayoum; concluded

Answer: B

• A) ✗ Wrong: “Who studied the ancient grain samples from the Fayoum” is essential (it tells us which researchers), so there is no opening comma — and a single comma here separates the subject from its verb.
• B) ✓ Correct: No punctuation: subject (“The researchers who studied … Fayoum”) → verb (“concluded”) → object (“that farming …”).
• C) ✗ Wrong: Two errors: a comma between subject and verb and a comma between the verb and its that-clause object.
• D) ✗ Wrong: A semicolon would need a complete sentence on both sides; the left side has no main verb.

Worked example 3 — label + name

Text: Rising water temperatures are a growing concern for fish farmers along the Nile. In 2015, ______ completed a study of how Nile tilapia respond to warmer water, and her results are now used by farms across the region.

Which choice completes the text so that it conforms to the conventions of Standard English?

• A) marine biologist, Hana Fouad
• B) marine biologist Hana Fouad
• C) marine biologist Hana Fouad,
• D) marine, biologist Hana Fouad

Answer: B

• A) ✗ Wrong: A job title directly before a name is not separated from it by a comma.
• B) ✓ Correct: “Marine biologist Hana Fouad” works like a title + name: no comma. The subject then goes straight to the verb “completed.”
• C) ✗ Wrong: The comma after “Fouad” separates the subject from its verb “completed.”
• D) ✗ Wrong: “Marine biologist” is a single job label; a comma between the adjective and the noun breaks it.

Worked example 4 — which-clause

Text: Alexandria was home to the most famous library of the ancient world. Today, the city has a modern successor. The Bibliotheca Alexandrina ______ opened in 2002 near the site of the ancient library, has space for millions of books.

Which choice completes the text so that it conforms to the conventions of Standard English?

• A) , that
• B) which
• C) , which
• D) that

Answer: C

• A) ✗ Wrong: “That” is never used with commas, and it introduces essential information. Here, the information is extra, closed by the comma after “library.”
• B) ✗ Wrong: The clause is closed by a comma after “library,” so it needs an opening comma too.
• C) ✓ Correct: “Which” introduces extra information, and the comma before it matches the comma after “library.” Remove the clause: “The Bibliotheca Alexandrina has space for millions of books.” ✓
• D) ✗ Wrong: No opening comma, and “that” cannot introduce information that is closed by a comma.

Practice

Twelve original SAT-style questions. Use the skeleton test and the removal test on each one.

All pages in this course

Start here

• The Digital SAT: Complete Overview
• Time Strategy and How to Attack Every Question

Craft and Structure

• Words in Context
• High-Value Vocabulary for SAT Reading and Writing
• Text Structure and Purpose
• Cross-Text Connections

Information and Ideas

• Central Ideas and Details
• Command of Evidence: Textual
• Command of Evidence: Quantitative
• Inferences

Standard English Conventions

• Sentence Boundaries
• Commas and Extra Information
• Colons, Dashes and Semicolons
• Subject–Verb Agreement
• Pronouns
• Verb Tense, Aspect and Finiteness
• Modifiers, Parallel Structure and Comparisons
• Plurals and Possessives

Expression of Ideas

• Transitions
• Rhetorical Synthesis (Student Notes)

Full practice tests

• Digital SAT Reading and Writing — Practice Test 1
• Digital SAT Reading and Writing — Practice Test 2
• Digital SAT Reading and Writing — Practice Test 3