misty_h
  Junior Editor

Hi! I agree with you that it can be confusing, especially concerning not knowing how many siblings, friends, etc. a person has based solely on the comma placements. But, provided the writer knows their grammar rules, as does the reader, we're able to interpret and glean additional unstated information off the simple use of commas...how neat is that?

So, that being said, these commas are related to restricted/nonrestricted appositives.

If you read a sentence that says, "My cat Oreo loves to go outside," you would be able to interpret that this person has more than one cat because there are no commas around the name Oreo. Oreo is essential information and can't be left out or you wouldn't know which cat was being referred to. (restrictive appositive = no commas)

So, if we use the same sentence but add commas: "My cat, Oreo, loves to go outside," the commas are telling you "Hey, this person only has one cat, its name is Oreo, and it likes to go outside." You could leave Oreo out of the sentence, "My cat loves to go outside," and you'd still know the writer is obviously referring to Oreo because that's her only kitty. (nonrestrictive appositive = commas)

Another example would be, as you stated, inserting essential or non-essential information such as:

"My third grade teacher, Mrs. Westbury, was a real hoot." We put commas around her name because it's not essential. We'd know my third grade teacher was a hoot -with or without her name added. The name is just additional information - nice to have but not necessary for clarity.

But if I say, "My teacher was a hoot." you'd ask, "Which one?" There's not enough of a clarifying description in that sentence, so I'd either need to add more information (such as 'third grade teacher'), or insert the name of the teacher I am directly referring to, which makes their name essential information (so no commas): "My teacher Mrs. Westbury was a hoot."

It's all learned. We, of course, don't know these right off the bat, and honestly, many writers these days disregard these rules, which is an unfortunate devolution of our grammar (in my grammar-nerd opinion). But when done correctly, it's like deciphering a magical code LOL. That's why I get a bit perturbed when I see sites write that these restrictive/nonrestrictive commas are just for decoration (either use 2 commas for balance or none at all, lalala...WRONG). There is a reason for them! It's just up to us to educate ourselves on why they are (or are not) there.

From the comment below mine, it seems this article has been updated since my original post, so a lot has changed. I agree with you though - the case 2 about John the painter still doesn't make sense. You use the comma after John's name to set off the 'who clause' which is providing additional information about John (he's a better painter than me). It's nonessential information so it could be left out and the sentence would more »

This article is incorrect and should NOT be used as reference. The commas are providing information and are not there just for emphasis as the author claims - at least this is true in American and British English writing. Any of our writing style guides, Chicago Manual of Style, AP, AMA, etc, will discredit what she's written. Using her example:

My friend John is a good painter. (No commas imply I have more than one friend so I need John's name as essential information that he is the friend I am referring to.)

My friend, John, is a good painter. (Commas imply I only have ONE friend so his name is non-essential and could be left out. Basically, if I said, "My friend is a good painter," you'd know I mean John since he's the only friend I have.)

This makes more sense with family members of course:
My mother, Joan, is an avid gardener. ( I only have one mother so her name can be left out and you'd know who I mean.)

My sister Betty likes cookies. (I have more than one sister, so I need Betty's name included so you know which one I'm referring to.)

My sister, Betty, likes cookies. (I just have one sister, so her name can be omitted -My sister likes cookies- and you'd still know it's Betty I'm referring to because she's my only sister.)

I'm a professional editor/proofreader, so these erroneous articles really tick me off. Please update so it's accurate. more »