Punctuation should be governed by its function, which in ordinary text is to promote ease of reading by clarifying relationships within and between sentences. This function, although it allows for a degree of subjectivity, should in turn be governed by the consistent application of some basic principles lest the subjective element obscure meaning.

—Chicago Manual of Style, 17^th Edition

 

Em dashes instead of commas, parentheses, or colons

The em dash, often simply called the dash, is the most commonly used and most versatile of the dashes. Em dashes are used to set off an amplifying or explanatory element and in that sense can function as an alternative to parentheses (third and fourth examples), commas (fifth and sixth examples), or a colon (first and second examples)—especially when an abrupt break in thought is called for.

He is a very quiet part of my life, a filter that has been draped over my world so long that I no longer notice how it colors my view, and yet there he always is, and very occasionally I notice him, glimmering like a sunspot in the corner of my vision—my dead brother.

In high school, writing an English paper, I used the metaphor of sculpture—my life a mound of clay, his a leaf pressed into it, then peeled away.

His first and middle names—Gabriel Ricardo—came from two angels, one in the Bible and one at the hospital.

My memories of that time—I was six when he died—have, by now, faded to echoes.

Twenty-one years after the fact, he’s less a person than a story—one I tell and tell and tell.

In photos, his large, ink-wet eyes—fringed with thick lashes—drift upwards, as if drawn toward a light no one else can see.

To avoid confusion, the em dash should never be used within or immediately following another element set off by an em dash (or pair of em dashes). Use parentheses or commas instead.

When he died—of complications from pneumonia (itself a complication of the cerebral palsy that stiffened his limbs and unfocused his eyes and feathered his cheeks with wisps of red)—I understood and I did not understand.

or

When he died—of complications from pneumonia, itself a complication of the cerebral palsy that stiffened his limbs and unfocused his eyes and feathered his cheeks with wisps of red—I understood and I did not understand.

 

Em dashes with other punctuation

In modern usage, a question mark or an exclamation point—but never a comma, a colon, or a semicolon—may precede an em dash. A period may precede an em dash if it is part of an abbreviation. (The occasional awkward result may require rewording.)

Perhaps I do remember—or is this an extrapolation from the photos I’ve seen?—the surprising density of his small body pinning me to the couch as I held him in my lap.

Gabriel died—he died!—and there was nothing I could do.

At the time of his death—on a Friday night, around 6:30 or 7 p.m.—I was sitting at the edge of a pool, feet dangling into the cloudy water, afraid to jump in.

If the context calls for an em dash where a comma would ordinarily separate a dependent clause from an independent clause, the comma is omitted. Likewise, if an em dash is used at the end of quoted material to indicate an interruption, the comma can be safely omitted before the words that identify the speaker.

Because I was born in a different country—the place where I might have grown up if we hadn’t moved to the United States seeking better treatment for Gabriel—I know what it is to live one life before, another after. The difference is that I can return to the country where I was born.

“You go—” my parents said to him, hovering over his bed. “You go on, if you need to. We’ll be all right.”

 

Em dashes with “that is,” “namely,” “for example,” and similar expressions

An em dash may be used before expressions such as that is or namely.

I dreamed of a black-haired woman who would grow enormous and burst through the roof and destroy our house—that is, me—if I let her inside.

Small, ordinary things—for example, watching a movie, falling asleep, or going to the bathroom by myself—grew frightening and impossible.

 

Em dashes in lieu of quotation marks

Em dashes are occasionally used instead of quotation marks to set off dialogue (à la writers in some European languages). Each speech starts a new paragraph. No space follows the dash.

—Are you OK?

—Yes.

 

Em dash between noun and pronoun

An em dash is occasionally used to set off an introductory noun, or a series of nouns, from a pronoun that refers back to the noun or nouns and introduces the main clause.

Perfection—that was what I strove for in all aspects of my life.

The green balloon, the pink suitcase, the small stuffed cow I hung in his tree—these are the fragments that remain with me, the talismans I polish to shining.

 

Em dashes for sudden breaks or interruptions

An em dash or a pair of em dashes may indicate a sudden break in thought or sentence structure or an interruption in dialogue. (Where a faltering rather than sudden break is intended, an ellipsis may be used.) If the break belongs to the surrounding sentence rather than to the quoted material, the em dashes must appear outside the quotation marks.

“I have”—and here I must perform a certain calculus, depending on whom I’m talking to—“two siblings.”

I had—have—a brother.

“Your brother—”

“Gabriel? Where is he?”

He was alive and then—