ACT English: Comma Rules for Appositives and Nonrestrictive Clauses

An appositive is a noun phrase that renames another noun. Example: "My friend Sarah" (if Sarah is the only friend, use commas: "My friend, Sarah, is here"). A nonrestrictive clause adds extra info but isn't essential to identifying the noun. Example: "My dog, which I got last year, is friendly." (The clause isn't needed to know which dog; commas are required.) A restrictive clause is essential to identifying the noun. Example: "The dog that I got last year is friendly." (Without "that I got last year," we don't know which dog; no commas). Key rule: Use "which" for nonrestrictive (nonessential) clauses; use "that" for restrictive (essential) clauses. When you see "which" or a name/noun being restated with commas, you've found nonrestrictive territory—always use commas.

Simple test: Remove the clause. If the sentence still makes sense and fully identifies the noun, the clause is nonrestrictive (use commas and "which"). If removing it creates confusion about which noun you mean, it's restrictive (use "that," no commas).

Mistake 1: Using "which" for a restrictive clause. "The book which I read yesterday" (wrong). "The book that I read yesterday" (right). Mistake 2: Omitting commas around a nonrestrictive clause. "My teacher, whom I respect, is retiring" (right). "My teacher whom I respect is retiring" (wrong). Mistake 3: Adding commas around restrictive appositives. "My sister, Emily" (wrong if you have multiple sisters; right if you have one). "My only sister, Emily" (right—"only" signals nonrestrictive). Mistake 4: Confusing who/whom. Use "who" for subject, "whom" for object. Both can appear in nonrestrictive clauses with commas. Mistake 5: Using commas with essential identifiers like proper nouns placed as appositives. "The scientist Albert Einstein..." (no commas; identifies who Einstein is). Before placing commas, ask: "Is this info essential to identifying the noun?" If yes, no commas. If no, use commas.

Quick check: (1) Is the phrase/clause essential or extra? (2) If nonrestrictive, use commas. (3) Use "which" for nonrestrictive, "that" for restrictive.

1. "My friend Sarah loves pizza." (One friend? Add commas: "My friend, Sarah, loves pizza.") 2. "The book that was on the table is mine." (Restrictive—correct, no change.) 3. "The book, which was on the table, is mine." (Nonrestrictive—correct, commas present.) 4. "My dad who is tall plays basketball." (Essential info—should be: "My dad, who is tall, plays basketball" only if you have one dad; otherwise, no commas.) 5. "Students which complete homework get A's." (Wrong "which"—fix: "Students who complete homework get A's.") For each, identify: Essential or extra? Use "which" or "that"? Place commas accordingly.

Daily drill: Write five sentences with appositives. Write five with nonrestrictive clauses. Place commas correctly. Then write five with restrictive clauses and verify no commas appear.

Comma rules for appositives and nonrestrictive clauses appear in 2-3 questions per ACT English section. These are straightforward grammar rules—once you know them, you never miss. Each question is worth 1 point, and correctly using commas signals polish and precision. Mastering these rules guarantees 2-3 extra points per test (10-15 overall) because they're entirely learnable and appear consistently.

Spend 2-3 days on these rules. Practice identifying appositives and clauses, then placing commas correctly. By test day, this will be automatic and you'll catch errors instantly.