A sentence fragment is an incomplete sentence. To avoid writing sentence fragments, make sure each sentence has a subject and predicate and expresses a complete thought.
Fragment: The fruit tart.
The fruit tart tasted sweet and delicious.
Fragment: Cub playing.
The cub was playing with the mother bear.
Fragment: The tall tree.
The tall tree is high above the forest ground.
A run on sentence is a sentence with two different thoughts. To avoid writing run on sentences, be sure to join two complete sentences with a comma and a linking word.
You may also write them as two separate sentences.
Run on: We ran and played on the field it was sunny.
We ran and played on the field. It was sunny.
Run on: Don't kick the ball in the house it's too dangerous.
Don't kick the ball in the house. It's too dangerous.
Run on: The children on the ride screamed loudly it hurt my ears.
The children on the ride screamed loudly and it hurt my ears.