En dash, em dash, hyphen: the three-dash problem in Australian style

Most of the manuscripts that cross my desk use one horizontal mark for three different jobs. A writer will hyphenate a compound, punctuate an aside, and indicate a page range with the same little dash, usually because their keyboard makes the shortest one the easiest to reach and the other two feel like a fussy distinction nobody actually checks. Somebody does check, and the distinction isn’t fussy — it’s the difference between three marks with three separate jobs, and getting it wrong is one of the more reliable ways to signal that a manuscript hasn’t had a proper style pass.

Three marks, one keyboard shortcut

The confusion has a straightforward origin. A standard keyboard has exactly one dash-shaped key, and it produces the hyphen. The en dash and em dash exist in every serious typeface but have to be typed in deliberately, through a menu, a shortcut, or an autocorrect rule — which means most writers only ever produce the version their software defaults to, regardless of which one the sentence actually needs.

The names come from traditional typesetting rather than grammar. An em, in metal type, was a unit of measurement roughly equal to the width of a capital “M” in the typeface being used, and the em dash was set to that width. The en dash, as Merriam-Webster’s own usage guide confirms, was set to the narrower width of a capital “N.”

Printers needed a long dash for stylistic breaks and a shorter one for connecting related items, and the two marks were built to different physical widths for that reason, long before anyone wrote a grammar rule to justify the distinction.

The hyphen, shorter again, was never part of that system at all — it comes out of word formation, not typographic spacing, which is why it behaves so differently from the other two.

What each mark is actually built to do

Set aside the history and the functional distinction is simple enough to hold in your head. The Chicago Manual of Style, still the clearest reference for the underlying logic even where Australian practice diverges from it, sets it out cleanly: a hyphen joins two elements that function as one — tie-in, toll-free, a well-known editor — where the words are working together as a single unit. An en dash connects things related by distance or range: pages 147–48, the May–September issue, or a prefix attached to an already-compound term like pre–World War II. An em dash does something else again — it breaks the sentence open to insert an aside, the way this clause is doing right now, and it can stand in for a colon or a set of parentheses depending on how hard the break needs to feel.

Confusing these isn’t a cosmetic slip. A hyphen where a range needs an en dash reads as one continuous, oddly formed word. An em dash where a simple hyphenated compound belongs looks like the sentence lost its thread halfway through. Readers register the wrongness even when they can’t name what’s wrong, which is exactly the kind of small friction that erodes trust in a piece of writing without the reader knowing why.

Where Australian style actually lands, and why it surprises people

Here’s the detail most Australian writers get wrong in the opposite direction from what they expect. Style guides that follow American convention typically favour a closed-up em dash for a mid-sentence aside — no spaces, straight into the surrounding words.

The Australian Government’s own Style Manual, the standard reference for government and much professional writing in this country, has moved the other way. For digital content, it recommends a spaced en dash for exactly the job the em dash traditionally did — setting off non-essential information within a sentence — and explicitly departs from the older print-era guidance that called for a spaced em rule instead. Part of the reasoning is accessibility: an unspaced en dash can be misread by a screen reader as a hyphen, so the space around it isn’t decorative, it’s functional.

That means a lot of Australian writers who learned “em dash for asides” from American style guides are following a convention their own national style manual has quietly moved away from for digital text. Neither choice is wrong in isolation — the manual itself says the main requirement is to pick one approach and apply it consistently through a document — but a manuscript that mixes closed em dashes, spaced em dashes, and spaced en dashes in the same piece is applying no convention at all, which is the actual problem an editor is fixing when this comes up.

The practical version of all this

None of it requires memorising typesetting history to apply. A hyphen joins; an en dash spans or connects a prefix to a compound; an em dash — or, in current Australian digital style, a spaced en dash — opens a break in the sentence for an aside. The specific choice between em and en for that third job depends on which style guide a piece is following, and the only real error is switching between them inside the same document without anyone deciding to.