Punctuation and typographic symbols

What is an em dash?

The em dash (—) is the longest of the common dashes, a line about the width of a capital M that marks a break in a sentence. Unicode encodes it as U+2014 EM DASH. The American Heritage Dictionary says it is named for the width of an m in printing, and the AP Stylebook calls it “about the width of a capital letter M”. Matthew Butterick’s Practical Typography adds that em and en are units of type measurement, not the letters, and that in digital fonts an em dash is typically about as wide as a capital H. The US Government Publishing Office’s Style Manual uses it to mark a sudden break or abrupt change in thought, an interruption or an unfinished sentence, and in place of commas or parentheses where that makes the meaning clearer. Butterick puts it where “a comma is too weak, but a colon, semicolon, or pair of parentheses is too strong”. Chicago sets it with no space on either side; AP puts a space on each side and simply calls it a dash.

TechCrunch reported in November 2025 that the em dash, by then treated as a telltale sign of text written by AI, had “popped up everywhere”, though it was not a reliable signal. The AP Stylebook’s editor, Anna Jo Bratton, had written that August that the tell “is not the em dash, which has been around for many years”.

Em dash or en dash?

The em dash sets words apart and the en dash (–) joins them. The en dash is about half as wide, named in the same way for the width of an n (American Heritage Dictionary), and Chicago’s CMOS Shop Talk notes that it is also called an en rule. It marks a range, as in 1880–1912 or pages 330–39, and a connection between pairs of words, as in Butterick’s Arizona–Nevada reciprocity. The hyphen is the shortest of the three. CMOS Shop Talk notes it is the only one with its own key on a standard keyboard, and Unicode notes that the keyboard hyphen-minus is used generically for a hyphen, a minus sign or an en dash.

British practice differs. The Guardian’s style guide says its dashes “should be en dashes rather than em dashes or hyphens”, and CMOS Shop Talk calls spaced en dashes “more common” in British style, where Chicago uses an unspaced em dash. The AP Stylebook has historically used no en dashes at all, because they didn’t translate correctly to newspapers that received the wire by teletype.

Reference marks

The asterisk (*) marks an omission, a reference to a footnote or, in mathematics, multiplication, and its name is from the Greek asteriskos, a diminutive of the word for star (American Heritage Dictionary). The GPO Style Manual sets the order of footnote symbols: asterisk, dagger (†), double dagger (‡) and section mark (§). Merriam-Webster adds that the dagger can mark a death date. The section sign is used when citing documents with numbered sections, as in 15 U.S. Code § 1111, and the pilcrow (¶) when citing numbered paragraphs; Butterick doubles either mark for a reference to more than one. The pilcrow began as a letter C, for capitulum, “little head”, which the rubricators of manuscripts gave a vertical bar and later filled in, as Keith Houston traces in Shady Characters. The bullet (•) is, in Merriam-Webster’s definition, “a large dot placed in printed matter to call attention to a particular passage”.

Copyright and trademark signs

The copyright symbol (©) is one of three forms of copyright notice in US law, with the word “Copyright” and the abbreviation “Copr.” (17 U.S.C. § 401). The US Copyright Office says notice is optional for works published on or after 1 March 1989, and the UK government says that whether a work is marked or not “does not affect the level of protection you have”. The trademark symbol (™) shows that someone claims a name or logo as a trademark. The US Patent and Trademark Office says it can be used before any application to register the mark is filed, and that the registered trademark symbol (®) is used once the mark is registered. These pages describe the marks and are not legal advice.

Where the ampersand and the interrobang came from

The ampersand (&) began as the Latin word et, “and”, written as one character: traditional ampersands, Butterick notes, take the shape of the letters et. Its name is “and per se and” run together. In early lists of the alphabet, Merriam-Webster explains, Z was followed by &, read “& per se, and”, meaning that & by itself is the word and. The interrobang (‽), a question mark and an exclamation mark in one character, is much younger. Martin Speckter, who ran a New York advertising agency, proposed it in his magazine Type Talks in the March–April 1962 issue (CreativePro), and its name joins interrogation with bang, printers’ slang for the exclamation mark (American Heritage Dictionary).

Keyboard characters

Seven pages are keyboard characters, most of them with jobs in computing. Ray Tomlinson chose the at sign (@) for email in 1971 and read an address as “user ‘at’ host” (NPR). The hash sign (#) is also the number sign and the pound sign, and the American Heritage Dictionary marks the name hash as chiefly British; Chris Messina first suggested the hashtag on Twitter on 23 August 2007 (Carnegie Mellon University). The tilde (~) is the accent over the n of Spanish ñ, and before a number it says the number is approximate (Vocabulary.com). The caret (^) is a proofreader’s mark for an insertion and, in Excel, the exponentiation operator. The backslash (\) separates folders in a Windows file path; Bob Bemer, whom the Computer History Museum calls “the father of ASCII”, brought it into computer character sets. The vertical bar (|), called the pipe, joins commands on a Unix command line so that each reads the previous one’s output (GNU Bash manual). NIST’s guide to the SI writes the degree sign (°) with a space before °C, as in 30.2 °C, and with none after a number of degrees of angle.