Let’s look at a few quick examples of correct semicolon and colon usage.

• Ex. One. I went to the grocery store to pick up a few items for dinner: corn on the cob, bell peppers, onions, and chicken.
• Ex. Two. My grandmother said it best: “Onions make everything taste better.”
• Ex. Three. I ran into my cousin at the grocery store; I hadn’t seen him in five years. 

In the first two examples, a complete sentence precedes the colon. A full and complete sentence must generally precede a colon. You’ll notice from example one that only a list, rather than a complete sentence, follows the colon. In general, a complete sentence does not need to follow a colon. The second example shows a quotation after the colon. These are perhaps the two most common ways that writers use colons. Colons are generally used to provide or call attention to a list of items or actions, a noun, a quotation, an example, or an explanation.

In example three, a complete sentence precedes and follows the semicolon. Semicolons are often used to join two separate and complete sentences that are related. In such an instance, the semicolon operates a bit like a period between the two sentences but also connects the sentences to show a close relationship. It shows a closer relationship than we would see if the two sentences were separated by a period. If you are using semicolons in this manner, use them sparingly because if overused they will make your writing clunky and difficult to understand. 

Let’s look at a couple more examples.

• Ex. Four. This evening, I am preparing to make a magnificent dinner: spicy, curry chicken; creamy, garlic potatoes; and cayenne corn on the cob. 
• Ex. Five. To me, the act of eating is sort of like sex: there’s a slow buildup to a fantastically messy but satisfying conclusion. 

What do you notice about example four? It has both colons and semicolons. If you think I’m crazy, just hold on! It will all make sense in a moment. I promise. In this example, semicolons are used like commas to separate items in a list. So why not use commas in this example? Using commas in this example would create a very confusing list that looks a bit like this: “spicy, curry chicken, creamy, garlic potatoes, and cayenne corn on the cob.” If you see the problem with that list, then congratulations! You are ahead of the curve on semicolon use. Use semicolons to separate items in a list when some of those items already contain commas. The list in example four calls the reader’s attention to the dishes I’m about to make for dinner. Spicy is not a dish. Creamy is not a dish. They are adjectives describing each dish. Using commas rather than semicolons in example four would lead the reader to believe that I am about to make spicy and creamy. However, the semicolons make it clear that the dishes I’m about to make are “spicy, curry chicken” and “creamy, garlic potatoes.” Semicolons provide clarity in the list.

Example five shows when colons can be used to connect two complete sentences. Colons can be used to connect two sentences when the second sentence summarizes, clarifies, or explains the first sentence. But don’t overdo this type of colon use because it can bog down your writing very quickly.

Here is an online test that will help you improve your semicolon and colon skills. Remember, semicolons and colons are not interchangeable. They serve distinct purposes and should be used sparingly. Now, go forth and practice those semicolons and colons.