For more about commas see our Punctuation Overview page.
There are a couple of other interesting bits when it comes to using commas. They have, I am sure, very technical explanations which will almost certainly be beyond the ability of us mere mortals to comprehend. However, they are not particularly difficult to put into practice, so here goes..
Use a comma when addressing someone or something directly in a sentence:
Dad shouted ”Get down, Megan!” when the dog jumped up at grandma.”Mum, can we have fish and chips for tea?”
Remember that commas can save lives…
When children say, ” Let’s eat, grandad.” it is much less sinister than when they say,”Let’s eat grandad…”
When however means “on the other hand” or “but” it is usual to separate it from the rest of the sentence with a comma.
Mum wanted to go shopping. However, dad took us to the cinema instead.
Sports day is cancelled, however, it will now be held on Tuesday.
When however means “in whatever way” then the comma is not needed.
However hard he tried, Peter could not beat his friend John at snooker.