The em dash has been called that, because it is as long as the letter m in what ever font you are using. The en dash is as long as the letter n. The hyphen is a bit shorter and thicker, and the minus sign is different, still. There are specific rules for when to use these differing punctuation marks. For most fictional writing, though, you will use the em dash.
The Em Dash Replaces Other Punctuation
You can use the em dash to replace commas, a colon, or parentheses, to separate words or phrases in a sentence. The em dash should be inserted automatically into a word document if you type ‘word hyphen hyphen word’ without any spaces. Otherwise, you may need to set up your own short-cut key to insert the em dash. The em dash generally does not have a space before or after it. Here are three examples. The first replaces a colon. The second replaces two commas, and the third replaces parentheses.
I believe all children should be taught the three R’s: respect, resourcefulness and responsibility.
I believe all children should be taught the three R’s—respect, resourcefulness and responsibility.
My grandchildren, the delight of my heart, are the most wonderful children in the world.
My grandchildren—the delight of my heart—are the most wonderful children in the world.
Odgen Nash (my favorite poet) wrote light verse with droll humor and unusual rhymes.
Odgen Nash—my favorite poet—wrote light verse with droll humor and unusual rhymes.
Another more recent use of the em dash is to show an unfinished sentence in dialog when writing fiction. Authors may use an ellipsis if the speaker just trailed off, but if the speaker has a sense of urgency, or if someone interrupted them, then an em dash is preferred.
“I sense something; a presence I’ve not felt since…” (The speaker leaves off the end of his sentence, as though unsure of speaking it aloud.)
“I sense something; a presence I’ve not felt since—” (The dialog could correctly be punctuated this way, too, especially if someone interrupts the speaker in the next line.)
Use the En Dash to Connect Numbers
The en dash expresses a “to” relationship, like linking two dates, or a range of dates, or a range of pages. The en dash is automatically inserted into word documents when you type ‘word space hyphen space word’. The en dash usually does have a space before and afterwards.
The term “Baby Boomers” refers to the people born in the post-World War II period from 1946 – 1964.
The class was assigned to read Chapter Four, pages 32 – 37.
He took a long sabbatical, from July – October.
A Hyphen is Used in Some Compound Words
The hyphen is slightly shorter than the en dash, and often thicker, although this varies depending on the font used. The hyphen is mainly used in compound words. Some words are always written with hyphens:
Take a good look at ten-year-old. This is hyphenated when it is used as a noun or noun phrase. (When there is no “s” on “year”.) But when you use ten years old as a predicate adjective (when there is an “s” on “years”) then there are no hyphens!
The eight-year-old knew his multiplication table perfectly.
The eight-year-old child knew his multiplication table perfectly.
The child is eight years old.
The baby is nine months old.
The nine-month-old was starting to walk.
All of the in-law words take a hyphen, all the time! Both in the singular and plural.
When two words are put together to create a new word, it is usually hyphenated. Once the new word becomes well known and popular, the hyphen eventually is dropped.
mass + produced = mass-produced
black + bird = black-bird (in the early 19th century, now we use “blackbird.”)
cruelty + free = cruelty-free
table + cloth = tablecloth
stage + coach = stagecoach
race + horse = racehorse
Hyphens are used in a compound modifier before a noun. Hyphens are not used if the modifier ends in -ly, or with proper nouns or proper adjectives. When unsure if a compound word requires a hyphen or not, consult a dictionary.
Here are some examples:
She is a well-respected teacher. (Well-respected is a compound modifier before the noun “teacher”, so it takes a hyphen.)
That teacher is well respected. (Well respected in this sentence is not a compound modifier, but just an adverb plus and adjective.)
The highly trained experts were on hand to answer questions. (Highly ends in -ly, so no hyphen is used.)
The North American continent includes Canada, the United States, Mexico and Greenland. (The modifier is a proper noun, so no hyphen is used.)
Traditionally, but less frequently today, the hyphen was used to indicate a break in a word when you ran out of room at the end of the line and had to put the rest of it at the beginning of the next line. And last, but not least, the hyphen is used in phone numbers, instead of an en dash. 202-456-1111. (Guess who’s house that is?)