An en dash (–) is a punctuation mark that is sometimes used to set off a phrase – such as this one – that occurs either within or at the end of a sentence. An en dash is so named because it is usually the same width as a capital "N," wider than a hyphen but narrower than an em dash (—). It has a wide variety of uses, including replacing the word "to" between a range of numbers, replacing a standard dash in hyphenated words and indicating a relationship between two things.
Originally, the width of this mark was defined as half the width of an em dash, another punctuation mark. The specific width of an en dash sometimes varies with the font used because it is usually equivalent to the width of the capital "N" in a given font. Further, some programs create en dashes that are equivalent to the lower case "n" in certain fonts. An en dash may also be called an "n dash," "n-dash," "n-rule" or "nut."
Traditionally, the most common uses of en dashes are within a range of numbers or to indicate a relationship between two words. When used within a number range, the en dash may separate dates, times, monetary amounts, years, page numbers or any other range of numbers that has both a finite beginning and a finite end. For example, an en dash might be used in place of a hyphen when stating that a toy is recommended for children aged 4–7.
When used to indicate a relationship, this mark can denote either collaboration or a contrast. For example, a collaboration between a university and the town in which it is located might be shown by stating that the "Western University–Anytown clean air campaign has been successful." An example of contrast would be when a newspaper reports that a team won a game by a score of 7–3, meaning that the winning team scored seven points and the losing team scored three. In all of these situations, the en dash usually abuts the numbers or letters it falls between, meaning that there are no spaces on either side of the mark.
In cases wherein an en dash is used instead of commas to set off a phrase within a sentence – such as now – spaces are not technically supposed to be present, but are usually used for ease of reading. It's important to note, that in cases of setting off phrases, many publisher styles use the em dash rather than the en dash. At one time, the hyphen, en dash and em dash all had specific uses. Today, however, they are generally used interchangeably.