Single quotation marks are hard. Lately, it seems they’re practically impossible. More and more I see professional editors and professionally published writing use them wrong.

To get an idea of how these little marks are confounding even professional users of punctuation, look at the following two sentences.

“Jessie just looked at me and said, ‘Goodbye,'” Ben said.

“That house is the Smiths’,” Stephanie said.

Note the punctuation at the end of each quotation. Care to guess which is correct? Is it the example where both punctuation marks come after the comma? Or is it the example in which the comma sits between the two other punctuation marks?

Answer: It was a trick question. Both are punctuated correctly.

The key to understanding these two examples lies in the fact that the Stephanie quote, unlike the Ben quote, does not contain a single quotation mark. It contains an apostrophe. But to punctuate sentences like these correctly and with confidence every time, you need a solid understanding how single quotation marks are used.

Single quotation marks are used to indicate quotations inside of other quotations. “Jessie said, ‘Goodbye,'” Ben said. This is Ben talking, so his words go in quotation marks. But because we’re quoting Ben quoting someone else, Jessie, we use single quotation marks to indicate the quote within the quote.

Theoretically, you could keep nesting quotations within quotations, alternating between single quote marks and double quote marks for every layer. But that’s rare and extremely messy. No one’s likely to write, “Ben said, ‘Jessie said, “Mark said, ‘Goodbye.’“‘” That’s correct punctuation. But it’s a nightmarishly confusing sentence the likes of which should be avoided at all cost.

Once you know how single quotation marks are used, you need to know how they’re used with periods and commas. Just like regular double quotation marks, a single quote mark always comes after a period or comma. (Don’t try to use logic here. It will only mess you up.)

For example, when quotes are placed around movie titles — an option used by many publishers that avoid italics — people figure that you shouldn’t insert a comma or period within those quote marks. So they write: We watched “Jaws”. In American English, that’s wrong. British English has different rules, but on this side of the pond, it doesn’t matter whether the period is part of the quotation. It always goes inside: We watched “Jaws.” The same is true for commas: We watched “Jaws,” screaming our heads off the whole time.

Question marks and exclamation points are different. Because both these punctuation marks add extra meaning to a sentence, logic matters: Have you seen “Jaws”? Here, if you put the question mark inside the quotes, it would appear that the movie title itself was a question, like “Who’s Afraid of Virginia Woolf?” So put a question mark or exclamation point inside the quote marks only if it’s part of the quotation itself. Put them outside if they modify the whole sentence: Have you seen “Jaws”?

Single quotation marks follow the same rules: Periods and commas inside, question marks and exclamation marks depend on whether they modify the whole sentence or just the quoted part. But the single quotes add another layer of confusion, which is why people so often mess them up: Ben said to Jessie, “We watched ‘Jaws’.” This is wrong. The period belongs inside both the single quote marks and the double quote marks: Ben said, “We watched ‘Jaws.'”

It’s crucial to distinguish between single quote marks and apostrophes. Often, these two punctuation marks look identical. But apostrophes function as part of the word, like when you drop a letter: We were talkin’. Or when you form a possessive: That house is the Smiths’. That’s why a period or comma comes after an apostrophe and not before.

The biggest secret to avoiding single-quote-mark mistakes: Go slowly. Take it step by step. Then you can more easily see how to arrange all the punctuation marks in your sentence.

— June Casagrande is the author of “The Joy of Syntax: A Simple Guide to All the Grammar You Know You Should Know.” She can be reached at JuneTCN@aol.com.