For as long as people have been sending out Christmas cards, people have been messing up the plural and possessive forms of their own last names. And until those cards are fully replaced by holiday holograms or some other technological wonder, I'll feel obliged every year around this time to help people navigate the potentially humiliating waters of those few words scribbled on greeting cards.

Here's what I'm talking about: Merry Christmas from the Wilson's! Happy holidays from the Gomez'! We're looking forward to spending time at the Jone's house. We're having the Morris's over this year.

Assuming that "Jone's" was a reference to people named Jones, every one of those greetings contains an error — a seriously humiliating error. And though the mistakes are different, they're all rooted in some surprisingly common confusion about plurals and plural possessives.

Here's how to rise above that confusion and always get these right.

Start by dividing names into two categories: names that don't end in S, Z or X, like Wilson, and names that do, like Morris and Gomez. Names that end in I, like Miceli, and Y, like Berry, do not get their own category. They're part of our first category because they work the same as all the other non-S-ending names.

Next, note the difference between a plural, a possessive and a plural possessive. This is where people get tripped up.

The plural means "more than one" and it never takes an apostrophe. To form the plural of any Category 1 name, just add S. One Wilson, all the Wilsons. One Miceli, all the Micelis. One Berry, all the Berrys. Those "I" names tempt us to insert an apostrophe, but none is needed before the S.

The Y names trip us up because most non-proper nouns that end in Y use a special ending to form the plural — I-E-S — such as berries. But proper names never change form. So Mr. and Mrs. Berry are the Berrys.

Category 2 names — the ones that end in S, Z or X — form the plural by adding E-S: One Jones, all the Joneses. One Gomez, all the Gomezes. One Delacroix, all the Delacroixes.

Notice how none of these had an apostrophe. The apostrophe comes into play when you want to show possession. But before you show possession, it helps to stop and ask yourself whether one person is doing the possessing or more than one. That is, is it a singular or a plural that you want to make possessive?

For both categories, form the singular possessive with an apostrophe plus an S. Mr. Wilson's house. Mrs. Gomez's gift. Joe Miceli's cooking. Jane Jones's party. Pete Berry's famous eggnog.

The only reason this is confusing is that you have, no doubt, seen those S, Z and X names handled differently. Some newspapers and other publishers form the possessive of those by adding just the apostrophe: Jane Jones' party. And you can do that, too. But because Jane Jones's party is equally correct, it's easier to have just one rule for all names, regardless of what letter they end with.

Form the plural possessive with an apostrophe only — no extra S, just tack it on right after the possessive S. The Wilsons' house. The Gomezes' gifts. The Micelis' visit. The Joneses' party. The Berrys' daughter.

If you notice how funny some of these look, you can see how this is not something you want to just follow your gut on. Instinct and guessing is what causes all those errors you see every year. To get these right, you have to be conscientious and methodical, always asking: Do I want a plural, a singular possessive or a plural possessive?

JUNE CASAGRANDE is author of "It Was the Best of Sentences, It Was the Worst of Sentences." She can be reached at JuneTCN@aol.com.