A run-on sentence is caused by combining two sentences without the correct punctuation. The most common run-on sentence is the comma splice. This is when two sentences are incorrectly separated by a comma.
I have to go to the shop I need to buy milk.
(two independent clauses/need either a conjunction or a full stop)
I have to go to the shop because I need to buy milk.
(conjunction/because)
I have to go to the shop. I need to buy milk.
(full stop)We are going for dinner, then we are going to the cinema.
(two independent clauses/comma splice)
We are going for dinner and then we are going to the cinema.
(no comma – conjunction/and)
Common mistakes with sentences.