Among the many paradoxes of 2020: As we near the end of this annus horribilis, the percentage of Americans who plan to send Christmas cards or holiday cards is greater than ever.

This is a short article about how to avoid mistakes that lots of people make in them, including a big, common, embarrassing grammar mistake.

Unfortunately, it's one of those mistakes that can make people think less of you, even if they can't put their finger exactly on what's wrong.

First, the growth. A survey by the online greeting card company Paperless Post found that 60 percent of users think they'll send holiday cards this year. That's up from 38 percent last year. 

Also, the New York Times reports that Etsy, the craft site, has seen "a 23 percent increase in searches for holiday cards in the last three months, compared with last year."

So prepare for a fuller mailbox than in the past, and consider this a reminder that you might want to send a card out yourself, if you don't usually. Besides staying in touch with friends and family, it's also a great opportunity to build a slightly more personal relationship with business colleagues. 

There's a lot of etiquette-related advice out there right now, suggesting that 2020 holiday cards might differ from other years in tone or content. 

Among the popular suggestions: Don't send a card that portrays your family flouting pandemic restrictions. Also, while humor is great, be mindful of the fact that some people on your list might have had a tougher year than you did.

But let's get to the big grammar mistake that you've probably seen people make many times yourself. It has to do with how to turn a singular proper noun into a plural one.

Here's the rule to remember: If you're sending a card on behalf of your family, and your family members all have the same last name, you form the plural of your name in most cases by simply adding an "-s" to the end.

For example, my last name is Murphy, so the plural form is, "the Murphys." For example, "Merry Christmas from the Murphys."

The exception is if your last name happens to end in "s," "x," "ch," "sh," or "z." In that case, you add an "-es."

So it's, "the Fernandezes," "the Sellerses," or "the Doriches," for example. 

Also, I know there are times when this grammar construction just looks weird. Frankly, the "-ys" at the end of "Murphys" always struck me as odd, even though it's grammatically correct.

Your easy solution in that case? Don't use a plural noun at all, and instead use your last name as a modifier: "Merry Christmas from the Murphy Family" or "Happy Holidays from the Smith Family."

Oh, and never, never, never add an apostrophe. That's a big mistake you've probably seen, and I think you'll agree it can mar an otherwise very nice and welcome holiday card. 

It's that simple: Add an "-s" unless your name already ends in one of the five letters or combinations listed above, in which case it's "-es."

Now you can go back to deciding whether a holiday card depicting your family in masks is perfectly tuned, or too cliché already. The jury's still out on that one.