A subject of endless fascination both from the technical and the creative points of view. We used to think a lot about the proper distinction between an en-dash and an em-dash. I can’t remember what it was — maybe just that one was favored in Britain and the other in America. Space around them was of vital import. Hart’s Rules, that charming compendium of all things book (Oxford style) clarifies the subject.

The en-rule (–) is used (a) to denote a span, e.g. ‘folios 23–94’; (b) to specify a period by connecting two terminal dates, e.g. ‘the 1939–45 Holocaust’; (c) between separate places or areas linked, e.g., in a political context, ‘the Rome–Berlin axis’; (d) between the names of joint authors to avoid confusion with the hyphen of a single double-barrelled name, e.g. ‘the Temple–Hardcastle project’ (that is the project of Mr Temple and Mr Hardcastle).

Em rules or dashes—in this and the next line an example is given—are often used to show that words enclosed between them are to be read parenthetically. In the following example the dashes help to clarify a somewhat involved sentence:

Early in August M. Krestinski, the Soviet Ambassador in Berlin, who in consequence of the incident had been—not recalled but—granted leave of absence, returned to his post.

Thus the punctuation of a verbal parenthesis may be indicated in three ways: by em dashes, by ( ), or by commas.

Omit the dash when a colon is used to preface a quotation or similar matter, whether at the end of a break-line or not.

The dash is used chiefly to mark an interruption in the structure of a sentence.

It’s reassuring to work in an industry which has cared so much about this sort of thing that years and years of informed decision-making gets written down like this, codified for the education of future generations of apprentices and copyeditors. However, the computer keyboard finds it hard to distinguish between en- and em-dashes; I used two hyphens to represent an en-dash and three to make an em-dash in the quotation above, though in the real world an en-dash would be half as long as an em-dash, not two-thirds*. An important distinction? Not really I guess; we could probably get used to recognizing that the text between a pair of double-hyphens is “to be read parenthetically”. I direct your attention to the bit about a Middlemarch em-dash in this piece by Kathryn Schultz in New York Magazine‘s Vulture blog  on “The five best punctuation marks in literature” — she means specific occurrences of punctuation usage, not her five favorite punctuation marks, like pilcrow, upside down question mark etc. (I think my favorite would be the exclamation point, which I cannot write without saying “bang!”)

The loss of these subtle distinctions of usage must lead to an impoverishment of meaning. Not perhaps huge, but no doubt occasionally significant. My current bugbear: the apostrophe used to designate the plural — which one begins to see more often than not in shops around this city — seems almost destined to become an accepted alternative. Context will mostly make it clear that we are not talking about the possessive, but confusion must potentially be the result in some contexts. The losses which the digital-ification of publishing will bring on us seem impossible to resist rather like looming species extinctions — “At least half of the tortoises and turtles, a third of the amphibians, a quarter of the mammals, and an eighth of the birds on this planet face a risk of extinction in the near future” (Verlyn Klinkenberg, New York Review of Books, 20 March, 2014). I guess we all just have to do our bit to slow progress down these slippery slopes.

* An em space is the same as the type size — in a 10 point font the em is 10pts wide and the en is half of that; in 14pt, the em will be 14pts wide etc., etc.