Around this time of year, I usually give out advice about how to avoid the errors people make forming plurals and possessives on their holiday cards.
You know, like how some people goof up and write "Merry Christmas from the Smith's" or "Holiday party at the William's" or "We'll be at Thoma's house." Or how they write "Wishing you the best of the season and all it's joys" or "Who's house will we visit?"
But this year, instead of giving constructive advice, I'd like to assign blame. There is, in fact, a culprit responsible for all these errors and more. It's the letter S.
The letter S is, I'm pretty sure, evil. It has too much power — too many special jobs to do — so it messes people up.
First, the letter S forms plurals. One cat, two cats. One shoe, two shoes. But you can't always count on it. You can't say one man, two mans or one box, two boxs. So in this, its biggest job, the letter S can let you down when you least suspect it.
The letter S also forms possessives. The cat's tail, the shoe's sole, the box's lid. For this job, it teams up with an apostrophe. But again, you can't just call on the letter S every time. Plural possessives usually use an apostrophe not followed by S: The cats' tails, the shoes' soles. Though, of course, irregular plurals do take the possessive S: men's accessories, children's books.
If that's not confusing enough, a proper noun that ends in S, like Lois or James, can form its possessive with or without another S depending solely on which editing style you're following. So in a newspaper you might see Lois' hat, but in a book you'd see Lois's hat.
Then, stooping even lower, the letter S likes to throw us a curve by forming possessive "its" all by itself, without the help of an apostrophe. So "The dog wagged its tail" takes no apostrophe.
But does that mean that "it's" with an apostrophe is always wrong? Nope. Because the letter S is also tasked with the job of standing in for our most common verb: is. We see this in contractions like "The cat's outside," meaning "The cat is outside." Or "It's hot outside," meaning "It is hot outside." Oh, and S can also be a contraction of "has," as in, "It's been hot all day."
Finally, the letter S is also how we conjugate verbs in the third-person singular. I walk, you walk, he walks, she walks, we walk, they walk. See how "he" and "she" get an S but the others don't?
Other languages don't have these problems. In Spanish, S makes plurals (un gato, dos gatos), but to show possession, Spanish speakers don't rely on S. They use "de," meaning "of" (el gato de Maria).
Italian doesn't even use S for its plurals. It has a different system in which cat, gatto, forms the plural with an I: gatti.
In English, the only way to navigate the minefield that is the letter S is to tread slowly. Ask yourself whether your noun is singular or plural, Smith or Smiths, before making it possessive: Mr. Smith's house or the Smiths' house. Remember that words that end with S usually form their plural with ES, the Thomases, and that plurals made into possessives take just the apostrophe: the Thomases' house.
Remember that "its" is possessive but "it's" is a contraction of "it is" or "it has." The same rule applies to "who's." It's exclusively a contraction: "Who's there?" If you want to show possession, you need "whose": "Whose car is that?"
Finally, don't confuse contractions with conjugated verbs. "Let's" means "Let us," but "lets" is used in "He lets the cat out at night."
JUNE CASAGRANDE is the author of "It Was the Best of Sentences, It Was the Worst of Sentences." She can be reached at JuneTCN@aol.com.