This usage of the comma has instigated arguments from writers and grammarians over the years. As much as those who use it have proven its necessity, not everyone has accepted its importance.
The comma before and (or or) is called a serial comma or Oxford comma (because it’s used by Oxford University Press). It is used before the penultimate (second from the last) item on a list consisting of three or more items.
It’s important to use some sentences as examples to see whether this comma is really necessary or it’s just overrated.
- He bought Sharwama, pizza, eggs and grits, and broccoli soup.
- He bought Sharwama, pizza, eggs and grits and broccoli soup.
The meaning portrayed in 1 is that ‘eggs and grits’ is one meal, different from ‘broccoli soup’. In 2, we are not sure whether ‘eggs’ is one of the things bought, different from ‘grits and broccoli’, or the combination of any two of the trio.
Look at another set of examples:
- I love reggae, jazz, hip-hop, and rock and roll.
- I love reggae, jazz, hip-hop and rock and roll.
1 shows that ‘rock and roll’ is a single genre of music, different from ‘hip-hop’; 2 might suggest that ‘hip-hop and rock’ is a genre, different from ‘roll’, or any other combination.
Let’s look at yet another example:
- We can tell any of the directors, Mr Achebe, or Mrs Olatunji.
- We can tell any of the directors, Mr Achebe or Mrs Olatunji.
1 shows that any of the directors is different from Mr Achebe or Mrs Olatunji because they are three separate people, but 2 suggests that Mr Achebe and Mrs Olatunji are the directors.
- He admires his teacher, Mahatma Gandhi, and Mario Puzo
Here, using the serial comma makes it clear that he admires his teachers and the other two individuals separately.
However, those who oppose the use of serial comma argue that rephrasing will bring an end to any misconceptions.
- He admires Mahatma Gandhi, Mario Puzo and his teachers.
On the whole, the necessity of the serial comma in the above sentences cannot be overemphasized. It clearly differentiates different entities that are listed together, without which a statement might become confusing.
Despite that, you can only use this comma where it’s acceptable.