Mark Twain’s encounter with a particular foreign tongue inspired an essay called “The Awful German Language.”

Welcome to a new feature of this column. We won’t call it “The Awful English Language.” Yet it will focus on challenges of English for all of us.

Many aspects of English work well. Some are harder than others.

Today’s topic is one of the keyboard’s smallest characters: The apostrophe. It works well and isn’t hard.

One of its functions is to take the place of omitted letters, such as in contractions.

That’s not what often causes confusion, except when “it’s” and “its” are mixed up. But that’s a problem with homophones — differently written words with the same sound — not just an apostrophe mistake.

What often causes confusion is another function: The possessive form. It shouldn’t cause confusion, because the rules are simple:

¯ To make a singular noun possessive, add an apostrophe and an “s” to the singular noun. The book belonging to Pat is Pat’s book. The tablets belonging to Moses are Moses’s tablets. The toy belonging to the child is the child’s toy. The offspring of the goose are the goose’s offspring. The car belonging to Dr. Smith is Dr. Smith’s car. The house belonging to Mr. and Mrs. Jones is Mr. and Mrs. Jones’s house. And the children of John and Mary are John and Mary’s children.

¯ To a make plural noun not ending in “s” possessive, add an apostrophe and an “s” to the plural noun. The toy belonging to the children is the children’s toy. The offspring of the geese are the geese’s offspring. Similarly, a public bathroom for men and boys is often called a “men’s room.”

¯ To make a plural noun ending in “s” possessive, just add an apostrophe to the plural noun. The toy belonging to the dogs is the dogs’ toy. The car belonging to the Smith family is the Smiths’ car. The house belonging to the Jones family is the Joneses’ house. Similarly, a public bathroom for women and girls is often called a “ladies’ room.”

It’s that simple. Some adjust those rules slightly and varyingly for particular words. But those are the simple rules. Nevertheless, confusion regarding apostrophes arises in multiple ways.

First, sometimes apostrophes are mistakenly omitted. The part of a department store selling clothing for children is not the childrens department. It’s the children’s department.

Second, sometimes the singular is used when the plural is correct. Next time you’re in a school, notice how pupils’ bathrooms are labeled. “Boys” and “girls” standing alone would be correct. However, the bathrooms are not the boy’s bathroom or the girl’s bathroom. Those would be for one boy and one girl. Instead, they’re the boys’ bathroom and the girls’ bathroom. They’re for all boys and all girls, respectively.

Elsewhere the school may list interscholastic-athletic records. They’re not boy’s or girl’s records. They’re boys’ and girls’ records.

Third, the difficulty sometimes arises with how to write plural forms. The plural of Jones, for example, is Joneses. So the plural possessive is Joneses’.

Fourth, sometimes apostrophes are mistakenly inserted into plurals that are not possessive. A greeting card from the Smith or Jones family is the Smiths’ or the Joneses’ card. However, when the card is signed as being from “The Smiths” or “The Joneses,” that is not possessive and needs no apostrophe.

When the Reagans moved to the White House, Life magazine ran a story on the new president and first lady, and included a photo of a gift to them. It was a mailbox labeled “The Reagan’s.” A letter to the editor shortly thereafter asked that the apostrophe please be removed from the Reagans’ mailbox, because it didn’t belong there.

Next time you’re invited to the Smiths’ or the Joneses’ house, and you see their mailbox has a similar apostrophe, you’ll know it’s not right.

Just don’t bring it up.

Randy Elf is a former foreign-language teacher.