Comma rules. For some, they are easy to remember. For others, they can be as difficult as assembling Ikea kitchen cabinets.
Every few months or so, we fight about the Oxford comma. The opponents: "That thing is pretentious". The supporters: "But it avoids misunderstandings".
The Oxford comma is the final comma in a list of three or more items. It is used before the conjunction that follows the final list item.The Oxford comma is not mandatory. Some style guides, for example, the AP style book for journalists, do not require the Oxford comma. The sentence below makes sense without it.
"Set the machine on a flat surface, unplug the cable and press the Reset button."
The sentence „I love my parents, Angelina Jolie and Brad Pitt“ could be interpreted as stating that you are the child of the two famous movie stars. In this case, we recommend the Oxford comma.
Plus, commas save lives. The following is a cliché, but we cannot resist:
"Anna enjoys cooking, her grandfather, and her cat."
"Anna enjoys cooking her grandfather and her cat."
This one is classic too:
"Let’s eat, Grandpa."
What happens if we omit the comma?
"Let’s eat Grandpa."
As I said, commas save lives.