ACT English: Tell Run-On Sentences Apart from Comma Splices

A comma splice joins two independent clauses with only a comma (no conjunction). Example: "I went to the store, I bought milk." A run-on sentence (or fused sentence) joins two independent clauses with no punctuation at all. Example: "I went to the store I bought milk." Both are wrong, but ACT tests them separately. Understanding the difference helps you pick the right fix instead of guessing.

Why the distinction matters: A comma splice can be fixed by adding a conjunction (and, but, or, etc.) after the comma, or by replacing the comma with a semicolon, period, or dash. A run-on can only be fixed by adding punctuation or a conjunction; you cannot use just a comma. Know which error you're facing and you'll eliminate wrong answers faster.

For comma splices: (1) Add a coordinating conjunction after the comma: "I went to the store, and I bought milk." (2) Replace comma with a semicolon: "I went to the store; I bought milk." (3) Replace comma with a period: "I went to the store. I bought milk." (4) Restructure into a single independent clause: "I went to the store to buy milk." For run-ons: (1) Add a period: "I went to the store. I bought milk." (2) Add a semicolon: "I went to the store; I bought milk." (3) Add a comma and conjunction: "I went to the store, and I bought milk." (4) Make one clause dependent: "After I went to the store, I bought milk." Recognizing these four fixes for each error type lets you evaluate all answer choices systematically.

Practice: Identify which error each sentence has, then list all four possible fixes. Example: "She studied hard she aced the test." Error: run-on. Fixes: (1) "She studied hard. She aced the test." (2) "She studied hard; she aced the test." (3) "She studied hard, and she aced the test." (4) "Because she studied hard, she aced the test."

Test 1: Is there a comma between two independent clauses? If yes, it's a comma splice. If there's no punctuation, it's a run-on. Test 2: Can you replace the error with only a period or semicolon? If yes, either fix works. Test 3: If a comma is there, is there a conjunction after it? If no, it's a comma splice that needs either a conjunction or a different punctuation. Use these three tests in order and you'll categorize every error correctly.

Drill six sentences: (1) "The weather was cold we stayed inside." (2) "The weather was cold, we stayed inside." (3) "The dog barked loudly and the cat ran away." (4) "The dog barked loudly the cat ran away." (5) "She loves coffee, she drinks it every morning." (6) "She loves coffee she drinks it every morning." For each, identify the error type, then write one correct fix.

Run-on and comma-splice questions appear on every ACT English section and are often combined into one passage section. If you can spot the difference, you eliminate half the wrong answers immediately. Most students treat these as the same error and guess; you'll use a systematic method and earn the point reliably.

Spend three days drilling the distinction using only the three-step identification test. By test day, you'll recognize these errors instantly and apply the right fix without hesitation. Each error you fix is one more point toward your target score.