Comma Splices: How to Fix Them on the Digital SAT

Quick Answer: A comma splice occurs when two independent clauses are joined by only a comma. To fix it, you can use a period, a semicolon, or a comma paired with a coordinating conjunction (FANBOYS).

pie title Common Punctuation Errors
    "Unnecessary Commas (Over-punctuation)" : 42
    "Semicolon vs Comma Splice Confusion" : 30
    "Dash Usage Errors" : 25
    "Other" : 3

What Is Comma Splices: How to Fix Them?

On the Digital SAT, the Standard English Conventions domain tests your ability to edit texts to conform to core grammatical rules. According to the College Board, mastering sentence boundaries is a critical skill for the 2026 Digital SAT format. A boundary error occurs when sentences are joined improperly, and the most common offender is the comma splice.

A comma splice happens when two independent clauses (groups of words that contain a subject and a verb and can stand alone as complete sentences) are shoved together with only a comma between them. While a comma indicates a pause, it is not grammatically strong enough to link two complete thoughts on its own. Understanding basic /sat/reading-writing/comma-rules-sat is essential because the SAT will frequently try to trick you by placing a comma where a stronger form of punctuation is required.

To fix a comma splice, you must use punctuation that acts as a hard stop, or you must add a connecting word. You can use a period, a semicolon, or a comma paired with a coordinating conjunction (such as and, but, or so).

Step-by-Step Method

1. Step 1: Identify the clauses. Read the sentence and look at the text before and after the comma in question. Check if both sides contain a subject and a working verb that form a complete thought.
2. Step 2: Check for a conjunction. Look immediately after the comma. Is there a coordinating conjunction (For, And, Nor, But, Or, Yet, So)? If not, and both sides are independent clauses, you have a comma splice.
3. Step 3: Choose a valid fix. Look at the answer choices for a proper grammatical boundary. You can replace the comma with a period, use a semicolon (reviewing /sat/reading-writing/semicolons-when-to-use is helpful here), or keep the comma but add a FANBOYS conjunction.
4. Step 4: Verify the flow. Read the chosen correction back into the sentence to ensure it creates a logical and grammatically sound sentence boundary.

Key Strategy

The most effective strategy for spotting comma splices on the Digital SAT is the "Period Test." If you see a comma separating two long parts of a sentence, imagine replacing that comma with a period. If both the first half and the second half could stand completely alone as their own sentences, then the original comma is creating a comma splice.

For example, consider the sentence: "The scientist analyzed the data, she published her findings." If you replace the comma with a period, you get: "The scientist analyzed the data. She published her findings." Since both are complete sentences, the original sentence contains a comma splice. You could fix this by using a semicolon or even evaluating /sat/reading-writing/colons-when-to-use if the second clause explains the first.

Worked Example

Question: The architecture of the new museum is highly unconventional, it features asymmetrical walls and an entirely glass roof that allows natural light to flood the main exhibition hall.

A) NO CHANGE
B) unconventional, and it features
C) unconventional it features
D) unconventional: and it features

Solution:

First, apply the Period Test to the original sentence. Clause 1: "The architecture of the new museum is highly unconventional" (Independent clause; it has a subject "architecture" and verb "is"). Clause 2: "it features asymmetrical walls and an entirely glass roof..." (Independent clause; it has a subject "it" and verb "features").

Because we have two independent clauses separated only by a comma, Option A is a comma splice.

Option C removes the punctuation entirely, creating a run-on sentence. Option D incorrectly mixes a colon with a coordinating conjunction, which is grammatically invalid for joining these clauses. Option B correctly fixes the comma splice by adding the coordinating conjunction "and" after the comma, properly linking the two independent clauses.

The correct answer is B.

Common Traps

1. The Semicolon Confusion — Based on Lumist student data, 30% of students can't distinguish when to use a semicolon versus a comma. A common trap is an answer choice that offers a comma where a semicolon is actually needed. Remember that a semicolon functions exactly like a period grammatically.

2. The "However" Trap — Our data shows that 38% of errors with transition words involve choosing a transition that doesn't match the punctuation logic. A classic SAT trick is writing: "The test was difficult, however, she passed." Because "however" is a conjunctive adverb and not a FANBOYS conjunction, this is still a comma splice. It must be written as: "The test was difficult; however, she passed."

FAQ

What exactly is a comma splice?

A comma splice happens when you connect two complete sentences (independent clauses) using just a comma. Because a comma isn't strong enough to hold two sentences together on its own, this creates a grammatical error.

Can I use a transition word like 'however' after a comma to fix a splice?

No, using a conjunctive adverb like 'however' or 'therefore' after a comma still results in a comma splice. You must use a semicolon or period before the transition word to properly separate the clauses.

What are the FANBOYS and how do they help?

FANBOYS stands for For, And, Nor, But, Or, Yet, So. Adding one of these coordinating conjunctions after a comma is a grammatically correct way to join two independent clauses and fix a comma splice.

How many Comma Splices: How to Fix Them questions are on the SAT?

Standard English Conventions makes up approximately 26% of the SAT Reading & Writing section. On Lumist.ai, we have 30 practice questions specifically focused on identifying and fixing comma splices.