Well that doesn't look right, you say to yourself at the part of the sentence with a complicated plural or possessive indication. Chances are you made an estimated guess as to the meaning behind those s's and apostrophes and let your editor sort it, right?
There are numerous ways plurals and possessives are written incorrectly, but I want to discuss the four that are the most common I see—and how to write it correctly if you're following along with the Chicago Manual of Style.
1. Plural for names that end in S
2. Possessive for names that end in S
2. Nouns that are both plural and possessive
3. Nouns that are collectively vs. individually possessive
Plural for Names That End in S
Pluralizing a name that ends with S (or X or Z) is probably the most straightforward, and most writers get it right. But I would be remiss if I didn't include it, since it's one of our favorite ways to call each other out on social media, particularly around the holidays. Plurals of names, most often done with last names or family names get formed by adding an S, but if it ends in an S, we add an E too. Here are some examples:
- A group of people named James: the Jameses
- Amelia Davix and family: the Davixes
- Natalia Rodriguez and family: the Rodriguezes
Possessive for Names That End in S
If there is an apostrophe toward the end of a name, chances are it's an indication that something belongs to them. It could also be a contraction for adding is or has to the name (but not was!), but that's not what we're here to discuss today. Here are some examples on making a name that ends in S (or X or Z) possessive. If you're following CMoS, to make any name that ends in S (or X or Z) even if that letter isn't pronounced, add an apostrophe and an S. Here are some examples:
- On Thursday nights, we go over to Jesus's for game night. (so at Jesus's house)
- Sometimes, Jane reaches over and scribbles on Marx's notebook when the teacher isn't looking.
- Rosa Martinez's shoes are the shiniest I've ever seen.
What if you want to give something to the Williamses, you ask?
Nouns That Are Both Plural and Possessive
Now that we've gone over some that are relatively simple, let's complicate it. Because why not? Sometimes we have nouns that are plural and we want to give them stuff. If the plural form of the word you're making possessive ends in an S, only add an apostrophe. If the plural form does not end in an S, add both the apostrophe and the S. Here are some examples:
- nurses' station
- men's room
- Joneses' backyard
Nouns That Are Collectively vs. Individually Possessive
This last one is what gets tripped up most of the time, in my experience. It's one of those errors that readers may not even notice, but to the readers who know the difference, the meaning of your sentence could change. Let's say you're talking about two characters at once, and one or both of them are given something. Where you put that apostrophe (and possibly S) to make it possessive makes a difference. If both names are possessive, the thing given to them are individual items. If only the second name is possessive, the thing is collective and belongs to both individuals. Here are some examples:
- her mom and dad's house -> The house belongs to both her mom and her dad. They share it.
- her mom's and dad's houses -> The houses are separate. One belongs to her mom and the other belongs to her dad.
- her mom's and dad's house -> This is grammatically incorrect. Two people are owning something but the thing owned is singular when it should be plural.