I’ve always had this question but I didn’t know the name for what I wanted to ask until just recently (figured it out while reading a tutorial for the Inform Interactive Fiction system).
When using commas in a list of things (see examples below) should there be a comma between the next-to-last item and the word “and”? I think it makes more sense this way (see examples below).
Example set 1:I like squirrels, cheese, and typographic design.
I like squirrels, cheese and typographic design.
To me, the second method doesn’t separate the two items, or indicate a pause (and the average reader would pause between “and” and “typographic design” regardless of whether the comma was there or not, right?).
The separation makes things clearer, in my opinion:
Example set 2:I like squirrels, cheese, and mashed potatoes and gravy.
I like squirrels, cheese and mashed potatoes and gravy.
It gets worse when the item containing “and” isn’t the last item:
Example set 3:I like squirrels, mashed potatoes and gravy, and cheese. I like squirrels, mashed potatoes and gravy and cheese. I like squirrels, mashed potatoes, and gravy and cheese.
In the second sentence in set 2, the terminal comma (is that even the right term for it?) is removed, and in the third sentence in set 2, it is re-inserted, but in the wrong place, drastically altering the meaning of the sentence. Read aloud, the sentences probably sound about the same, but I think I like the extra clarity added by the terminal comma, but see many texts in which it is omitted.
Is the terminal comma proper punctuation?
First, I don’t know whether there is a specific name for the comma in question, but when I read terminal comma in your question, I thought you were suggesting that there might be a comma (instead of a full stop) at the end of a sentence.
In answer to your fundamental question, there is no right or wrong way here. Some people prefer to put a comma before the last item and some prefer not to. I don’t know whether there is a UK – US split on preferences here.
The important thing is that when there is ambiguity as in your Examples 2 & 3, you should include a comma to make it clear what you mean.
If you have a simple list with no ambiguity, then the comma is optional.
If it’s a list of clauses or long phrases (instead of short single-word or 2/3-word items), then it often makes it easier for a reader if you put a comma before the final item.
So, in summary, if it makes it easier for the reader, or if it is necessary to clarify the distinctions between multiple items (especially where the items include the word ‘and’), then put a comma in. If it’s not necessary for intelligibility, then it’s optional and up to individual style.