You can go your whole life without needing these two. HOWEVER, if you are an Indie-pubbed (my shorthand term) author doing it all yourself, you have need to know. These punctuation marks are also called the En Dash and the Em Dash.
As set forth in earlier posts, my style guides—as a freelance corporate copy editor and as an author—include Webster's 11th edition and the Chicago Manual of Style 15th edition (or more commonly called the CMS, used for both novels and nonfiction work). You may need a medical-based style manual or, if you write for newspapers, you will be using the Associated Press Stylebook aka the AP Stylebook. Choose yours. No matter the reference guide, there are still unifying guidelines throughout. Like using nouns, verbs, punctuation marks. Like if you are a U.S.–based English-speaking person, spelling book as B-O-O-K.
For those of you interested, the N-dash along with the M-dash can be found within MSWord's word processing system under the Insert tab, then choose Symbol and finally click on the Special Characters tab. The regular old dash we all use to make hyphenated words is the shortest. Then the N-dash is a little longer, but the M-dash is the longest. You may have used one without knowing it. Anytime you have used a double dash to add in a side thought, well, you were using the shorthand typing version of the M-dash.
Here's an example of where each should be used:
Hyphen: He is one good-looking guy.
N-Dash: The verse can be found at James 1:1–3.
Also N-Dash: A North Dakota–style cold front struck our southern city.
M-Dash: She was young and tanned and probably weighed 120 pounds—oh, for the day when my scale stopped there!
Also M-Dash: "I just thought—" she bit her lip "—that you cared for me."
So hyphens we probably all know how to use within the grammatically correct sphere, or can confirm with a quick check of Webster's.
If you are with a big or little publishing house, their production department works with the design of the books and the special characters, so they will have people to change any misused hyphens to their proper N-dash or M-dash punctuation before the manuscript is printed.
Again, if you are both the publisher and the author of your Indie works, then here's the scoop:
The N-dash is used for numbers (like the Bible verse quoted above) or for two-word proper nouns being modified into an adjective grouping (like North Dakota–cold being used as an adjective.)
The M-dash is for those off-tangent thoughts, to set them apart from the main line of thinking. The M-dash can also be used within dialogue (see above) in place of the ellipsis (that three-dot punctuation mark that denotes a longer pause than say a comma and probably an interrupted speech pattern, either cut short by the speaker or by another person).
Webster's remains a monster go-to reference guide and, I'll repeat from yesterday's post, it gives a short grammar lesson when you look up "apostrophe."
The difference in the length of each of these dashes is miniscule, yet I think it serves a great function. Even if our eye registers the three of them as "alike," I think our brain connotes the difference and gives each its own weight. Like the shortest one, the hyphen, the dash, makes two-word combos into, essentially, one word. Our readers skim over them just like the word "a."
I believe the N-dash is there to cause our neurons to take note, to take just a jot's pause to realize we may have read the location for looking up one verse, but it is actually the span of several. Or to give our northern-based readers cause to smile when they read of a North Dakota–cold weather front hitting the South. And the big one—the M-dash. Shows us to take a moment to shift gears.
Our English grammar rules really do serve a function. Like well-placed commas tell a reader when to pause and a period when to stop, then move on. Isn't it wonderful that we can communicate to our readers "watch out, missing letter(s) here" by the simple use of an appropriately placed apostrophe. It kind of boggles the mind. Like the order of the universe. But that's just it in a nutshell. Order. So consult your reference guides, or hire a qualified freelancer, and keep on learning.
P.S. See today's additional Quote below, courtesy of Michelangelo. It is so appropriate. He states "I am still learning." So true!