Some writers may write sentences that contain two complete ideas, punctuated only with a comma or with no punctuation at all. Both are wrong.

A complete sentence (also known as an independent clause) is a sentence that can stand on its own.

A "run-on sentence," or a "comma splice," occurs when two complete sentences are written together with no punctuation or with only a comma to separate them.

Run-on sentence

She walked the dog he fed the cat.

Comma splice

She walked the dog, he fed the cat. 


Run-on sentence 

I’ve always wanted to go to Reno it’s wonderful there.

Comma splice

I’ve always wanted to go to Reno, it’s wonderful there. 


Run-on sentence 

My father designs and installs wind turbines he travels all over Saudi Arabia as an energy consultant


Notice that we have two ideas in two independent clauses:

  1. My father installs and designs wind turbines.

  2. He travels all over Saudi Arabia as an energy consultant.

To fix a run-on sentence, determine where one MAIN IDEA ends and another one begins.


1. Insert a period to make the two complete sentences separate.


She walked the dog. He fed the cat.


2. Insert a semicolon. Only use a semicolon if the two sentences are closely related.


I’ve always wanted to go to Reno; it’s wonderful there.


3. Add a word such as “and” or “therefore” after inserting a comma or a semicolon. 

These words will need a comma before the word: and, but, for, or, nor, yet, so. Words such as “however,” “nevertheless,” “therefore,” “finally,” etc. will need a semicolon and a comma.


She walked the dog, and he fed the cat.
I’ve always wanted to go to Reno; however, I haven’t gone yet.