The PeriodThe period is the ultimate and strongest form of breaking punctuation, which is why it’s known as a “full stop” in the UK. It is placed at the end of the sentence to indicate an end to that statement and a transition to a new one.
The comma is used to provide a bridge between very closely related statements or between sequences of incomplete statements. You’ve probably noticed that proper comma usage can be very tricky to master, and you’re not alone in that experience. We’ve covered some of the depths and complexities of comma usage in several posts, but for now what you need to know is this: the comma connects closely related thoughts, and the period separates finished, more-or-less unrelated thoughts.
The SemicolonThe other forms of breaking punctuation fall on a spectrum between the comma and the period. The semicolon is halfway between the two; it generally separates statements that could be broken into individual sentences, but which the author wants to be connected in the mind of the reader. Use it sparingly—it tends to create sentences that are very long and difficult to follow.
The ColonThe colon serves the specific purpose of introducing information; it can only be used if the text preceding it says something along the lines of, “I am going to tell you this.” So, for instance:
Gary picked up all of the items on the list: a pickaxe, a jump rope, and—for some reason—a huge container of lard.
This is what I was sent to tell you: that you must put an end to your company’s project, or your world will be destroyed.
You have chosen the greatest hamburger of all: the Beefinator.
Remember: the colon should only be used if the text before it is somehow introducing the text that comes after it.
The Em DashThe em dash is the jack of all trades. It swings back and forth between the comma and the semicolon and the colon. It can be used in place of a comma to provide a little more emphasis to the pause between related information, or in place of a semicolon to provide a little more connection between statements. It can also serve as a sort of weak colon, separating an initial statement from another that provides more connected or explanatory information. Often, I’ll simply use it to create variety when I’ve already used several commas or semicolons. But be careful about using it too much—the em dash is wide and easily noticeable, and a cluster of them in the same area of the page will tend to stand out garishly.
In summation, the comma is weakest form of breaking punctuation, used to separate closely related information; the semicolon separates weakly related or unrelated statements; the colon separates introductory text from the information it’s introducing; the em dash can serve as a strong comma, a weak colon, or a weak semicolon; and the period is the full stop that means that the previous statement is complete and we are moving on to something else.
It may seem like there is considerable overlap between the uses for these breaking punctuation marks—that’s because there is. Often, you’ll be able to use either a period or a semicolon; in other cases, either a colon or a semicolon or an em dash would work. What punctuation you choose should depend on how connected you want the information it breaks apart to be, on how much you’ve already used each form of breaking punctuation, and on how you want the sentence or sentences to flow. That is the reason for this post—to let you know how the breaking punctuation can be used, so that you know what your options are when you have more than one.
If you want some helpful homework, go back over this post again and pay particular attention to the breaking punctuation. You’ll notice that I’ve used each form of breaking punctuation at some point, and in just about every way they can be used. Find each point where I’ve used a breaking punctuation mark, and make sure you understand why I chose that particular mark at that point in the text. Good luck!