Commas signal to your reader to pause very slightly while reading. This can help make the individual parts of a sentence clearer in meaning. It also shows how sentences are split up, and separates words in a list.
A common mistake in writing is to place a comma where in fact a full stop is needed. This creates an over-long sentence. This misuse of the comma creates what is called a 'comma splice'. Aim to avoid comma splices in your writing.
When you proofread your work, highlight each comma and decide whether it is needed, or whether a full-stop would be more effective.
Look at the example below:
The room filled with smoke, I froze in panic.
This is an example of comma splice. The comma in the middle should not be there because each half is a complete sentence in its own right.
So in fact you should use two full sentences, each ending with a full stop. This makes for two shorter but much livelier, sentences:
The room filled with smoke. I froze in panic.
Alternatively - you could use a conjunction (joining word) to connect the two sentences:
The room filled with smoke and I froze in panic.
OR – when the two sentences are closely linked in some way, you could use a semi-colon:
The room filled with smoke; I froze in panic.
Identify the comma splices in the following piece of writing. As you find each comma think about what would happen if it were replaced with a full stop. Remember that the two sentences each side of a full stop must be meaningful and complete.
I was nervous, making my way through the crowd in the darkness. Lights glistened in time to the music, I blinked at the brightness. Fetching a drink from the corner, I looked at the food on offer. It was a pretty good spread, Hollie had really made an effort. It was just a shame that her mum had made a massive princess cake. The thing was wonky, but the creepy smile on its face was the worst part.
Lights glistened in time to the music, I blinked at the brightness.
It was a pretty good spread, Hollie had really made an effort.
These are both examples of comma splicing. A full stop, semi-colon or conjunction is needed for the sentences to be grammatically correct.