The Oxford Comma.

Grammar  Last time I attempted to use what I now find is called the "Oxford comma" was at school.  I was told it was wrong, I'd love marks, and I haven't used it again. There are some circumstances when it could be quite useful:

"The Oxford comma (also known as the serial comma) is that extra comma that you sometimes get at the end of a list, before the and or the or. “She wrote novels, essays, and JavaScript” uses an Oxford comma. “He bought apples, butter and the ranch” doesn't."

The Oxford moniker derives from the century-old endorsement of the serial comma by the Oxford University Press manual of style; and the OUP is backed up by a slew of revered authorities: Strunk's Elements of Style, Fowler's Dictionary of Modern English Usage and the Chicago Manual of Style. Why? Because omitting the Oxford comma can result in distressing double meanings:

“She lives with her two children, a cat and a dog.”

Despite that I still would use it. I'd probably rewrite that sentence to make it clearer:  "She lives with her two children and two pets, a cat and a dog."  You could even argue for some brackets around the animals [via].