How are commas used?
Commas alone cannot join two complete sentences. However, a comma combined with a coordinating conjunction can join two complete ideas of equal weight and importance.
When combining sentences…
Use coordinating conjunctions with a comma
Such as and, but, or, so, for (meaning “because”), and yet (meaning “but”)
- My dog is old. My cat is still a kitten.
- My dog is old, but my cat is still a kitten.
Common errors are…
Using comma splices
Comma splice refers to two sentences joined by a comma without the following coordinating conjunction.
- My dog is old, my cat is still a kitten.
- My dog is old, but my cat is still a kitten.
Using run‐on sentences
A run-on sentence refers to two sentences connected by a coordinating conjunction without the preceding comma.
- My dog is old but my cat is still a kitten.
- My dog is old, but my cat is still a kitten.
Using fused sentences
A fused sentence refers to two sentences connected without a comma or a coordinating conjunction.
- My dog is old my cat is still a kitten.
- My dog is old, but my cat is still a kitten