What is the origin of various symbols used in English, and when is the use of each appropriate? Here’s a guide to twelve common signs, including how they developed and in which contexts they are used or avoided.
1. & (Ampersand)
The ampersand was, at least until well into the nineteenth century, treated as the twenty-seventh letter of the alphabet, but its star has fallen, so that now it is used only informally except in registered names of businesses (“Ay, Bee & See Inc.”), which should be written as rendered; a comma preceding it is extraneous.
The symbol comes from the cursive formation of the Latin word et (“and”), and the name is a slurring contraction of “and per se and,” which used to terminate schoolroom recitals of the alphabet: The phrase means “and by itself and”; instead of reciting, “. . . W, X, Y, Z, and,” children said, “. . . W, X, Y, Z, and per se and” to clarify that “and” referred to a list item rather than serving as a conjunction for an item that was left unuttered. The symbol is also seen in &c. (“et cetera”), an alternate form of etc.
American Psychological Association (APA) style allows the ampersand to link author names in an in-text citation (“Laurel & Hardy, 1921”), but other style guides call for using the word and.
2. * (Asterisk)
The asterisk is used to call out a footnote or to refer to an annotation of special terms or conditions, to substitute for letters in profanity (“Oh, s***!”) or a name rendered anonymous (“the subject, M***”), to serve as a low-tech alternative to a typographical bullet, or provide emphasis in place of boldface (“Do *not* go there — the food is awful.”). It also has many specialized technical usages. Its name is derived from the Greek term asteriskos, meaning “little star,” and it was originally applied to distinguish date of birth from other references to years.
3. @ (At Sign)
Until the age of e-mail, the at sign was restricted mostly to commercial use, in purchase orders and the like, to mean “at the rate of” (“Order 1K widgets @ $2.50 per.”). It’s also used in displays of schedules for competitive sports to identify the event venue. Now it’s ubiquitous in email addresses and in social-networking usage, as well as computer protocols, but outside of those contexts, it is considered inappropriate for all but the most informal writing.
4. ¢ (Cent)
This symbol for cent (from the Latin word centum, meaning “hundred”), unlike its cousin the dollar sign — it’s also used in many monetary systems other than that of US currency — is rare except in informal usage or for price tags. When it does appear, unlike the dollar sign, it follows rather than precedes the numeral, though as in the case of the dollar sign, no space intervenes. The equivalent usage in a context where dollar signs are employed is to treat the amount as a decimal portion of a dollar (“$0.99”); for clarity, a zero should always be inserted between the dollar sign and the decimal point.
The sign probably originated to distinguish an ordinary c from one denoting a monetary amount.
5. ° (Degree Sign)
The sign for degrees of arc or degrees of temperature, which started out as a superscripted zero, was chosen for consistency with use of the minute (′) and second marks (″) employed in geometry and geography; those symbols originally stood for the Latin numerals I and II. The degree sign appears in technical contexts, but in general-interest publications, the word degree is generally used.
In references to temperature, the symbol (and the designation of the temperature scale) immediately follows the associated numerical figure (“45°C”). This style is true of many publishing companies, though the US Government and the International Bureau of Weights and Measures prescribe a space between the number and the symbol (“45 °C”), while other publications omit the first letter space but insert another between the symbol and the abbreviation (“45° C”).
6. ” (Ditto Sign)
The ditto sign, first attested three thousand years ago, signals that text shown above is to be repeated, as in a list in which the same quantity of various materials is intended to be expressed:
The word ditto, meaning “said,” derives from the Tuscan language, the immediate ancestor of Italian, but was borrowed into English hundreds of years ago. The word, its abbreviation (do.), and the symbol are considered inappropriate for most writing, though the term has often been used in informal spoken and written language to mean “(the same as) what he/she said.” Although the symbol has a distinct character code for online writing, straight or curly close quotation marks are usually employed to produce it.
7. $ (Dollar Sign)
This symbol for the American dollar and many other currencies was first used to refer to the peso, which inspired the American currency system. Various origin stories for the symbol come in and out of fashion, but it’s most likely that it developed from an abbreviation of pesos in which the initial p preceded a superscript s; the tail of the initial was often superimposed on the s. A dollar sign with two vertical lines is a less common variant.
Most books and other formal publications tend to spell out dollars in association with a (spelled-out or numerical) figure, but periodicals usually use the symbol, as do specialized books about finance or business or others with frequent references to money. In international publications, when the symbol is used, for clarity, it is combined with the abbreviation US (“US$1.5 million” or “US $1.5 million”).
The dollar sign is also used as an abbreviated reference to various functions in computer programming and similar contexts.
8. # (Number or Pound Sign, or Hash)
This symbol evolved from the abbreviation for pound, lb. (a literal abbreviation for the Roman word libra, meaning “balance”), in which horizontal lines were superimposed on the vertical lines of the letters, producing something like the tic-tac-toe pattern used today. One of many other names for the sign, octotherp (also spelled octothorp or otherwise), was a jocular coinage by telecommunications engineers in the mid-twentieth century. The symbol is seldom used outside informal or highly technical or otherwise specialized contexts.
9. % (Percent)
The sign for indicating percentage developed in the Middle Ages over the course of hundreds of years, beginning as an abbreviation of percent (from the Latin phrase per centum, meaning “out of a hundred”). Its use is recommended only in technical contexts or in tabular material, where space it at a premium. (Some standards authorities call for a space between a number and this symbol, but most publications and publishers omit the space.)
10. ~ (Tilde)
The tilde is used as a diacritical mark over various letters to indicate a variety of sounds in different languages, but it also appears midline, like a dash (and is sometimes called a swung dash), to denote “approximately (“Last night’s attendance: ~100”). It has technical connotations as well and is even used as a notation for recording sequences of action in juggling. The name, borrowed into English through Portuguese and Spanish from Latin, means “title.”
11. / (Slash, Solidus, Stroke, or Virgule)
During the Middle Ages, this sign of many names, including those listed above, served as a comma; a pair denoted a dash. The double slash was eventually tipped horizontally to become an equal sign and later a dash or hyphen. (The equal sign is still used as a proofreader’s mark to indicate insertion of a hyphen.) The slash — also called the forward-slash to distinguish it from the backslash, which is used only in technical contexts — is an informal substitute for or.
12. _ (Underscore or Understrike)
This artifact from the era of the typewriter was used on such devices to underline words to indicate emphasis in lieu of italics. As a survival of that function, words are sometimes bracketed by a pair of single underscores in email and other computer contexts to mark a word for emphasis (“That band totally _rocked_ the place.”). Indeed, as I typed this post in Microsoft Word, the program automatically converted rocked to italics. The symbol also appears frequently in email and website addresses and other technical contexts.