Have you ever come across the ‘Oxford comma’? If you haven’t, here’s a short explanation. When you have a list of three or more items it is normal to separate the items with a comma: ‘The coat came in blue, white, black, red and green.’ But the ‘Oxford comma’ means adding an extra comma between the last item on the list and the word ‘and’ as in: ‘…blue, white, black, red, and green.’