Parentheses and brackets (specifically, square brackets) normally come in pairs, as do other types of brackets and braces. Their main job is to set things off from their surroundings.

Apostrophes, like quotation marks, hang out far above the baseline, where they have two main roles: contraction and possession. They also occasionally have a third role: as a marker of the plural.

Semicolons, when they’re not winking at you, can be a useful punctuation mark. Some writers are fans of the mark; others could do without it. But whatever you think of semicolons, it can be helpful to know how they’re used.

The punctuation mark that many of us know as the slash appears on standard computer keyboards. But even though it sits right there next to the period and the comma—and though it was once used as a form of sentence punctuation like those marks—the slash is comparatively uncommon today in ordinary prose.

Dashes—specifically, en dashes and em dashes—are like hyphens, but longer. And though there’s some overlap in how hyphens and dashes are used, dashes play a role all their own.

Periods are small but powerful. Not only do they bring entire sentences to a stop with a single dot, they’re also commonly found in abbreviations and numbers.

Commas play at least two main roles in ordinary prose. They can set off words, phrases, and clauses—including direct quotations, questions, and thoughts—from the surrounding sentence. And they can be used between coordinate adjectives and other items in a series.