Colons and semicolons pack a lot of punch into a tiny, pencil-thin frame. Think about it: As writers, how many times a day do we rely on the colon or its laid-back cousin, the semicolon, to set off a witty remark or ensure that an impactful statement gets the attention it deserves? The colon and semicolon are indispensible little punctuation marks that we use all the time — albeit, often incorrectly. Writer, when was the last time you checked to see if your colon is functioning properly? It’s time for a grammatical colonoscopy.

Writer, meet the colon.

It’s an authoritative set of two dots stacked on top of each other, and it immediately signals that something major is about to happen. Although the colon gets around (it’s used to express time, punctuate an opening of a letter, and to cite laws), its main gig is to hang out at the end of a complete sentence and do one of the following things:

• Introduce a list

There are many things that captivate me: 1950s movies, chocolate, modern art and the city at night.

• Transition to a second sentence that explains, defines or connects to the first sentence, without using conjunctions

I’ll tell you why I hate winter: the snow always keeps me from wearing my favorite heels.

• Signal the reader that what follows deserves a lot of emphasis

And at that moment, I discovered what I had been searching for all these years: A city where it’s sunny, even in the winter.

To capitalize or not to capitalize?

Good question. There’s disagreement among the major grammar guides as to when you should capitalize the clause following your colon. Here’s the rule that The Chicago Manual of Style and Write In Color both follow (and you should, too!).

Capitalize after a colon when that colon is introducing either a quotation or more than one sentence.

I’ll tell you why I hate winter: The snow always keeps me from wearing my favorite heels. Also, there are fewer sunny days in the winter months.

Writer, meet the semicolon.

It’s the laid-back cousin of the colon that looks like a dot with a comma underneath it. When you see this punctuation mark, it usually means that there is an implied relationship between the complete sentences you’re reading. The semicolon can help you imply ironic relationships, opposing relationships, close relationships, or any other kind of relationships you see fit. That makes it one of the most versatile punctuation marks around.

If it helps, think of the semicolon as a weaker, more easygoing version of the period: it separates two independent clauses just as a period would, but still keeps them connected as part of one sentence. Here’s when you would call upon the semicolon:

• To join two closely-related sentences without using a conjunction

My friend never goes out in the snow; she’s afraid she’ll catch cold.

• To join two closely-related sentences while using a transition

I live in Los Angeles; my mother, however, lives on the East Coast.

• To create order in a confusing list that may already include commas

I live near my brother, Danny; my friend Alice; my sister, Lisa; and my cousin Todd.

To capitalize or not to capitalize?

The answer is simple: don’t capitalize the word following a semicolon unless it’s a proper noun that should always take a capital, anyway. (And as that last sentence illustrates, don’t capitalize the word after a colon unless there is more than one complete sentence following it!)

Now that you have the basic rules, give your writing a quick colonoscopy. Are your colons and semicolons functioning as they should in your latest poem, play or prose? Even if all your punctuation systems are working correctly, think of ways that the seemingly petty colons and semicolons can infuse color into your writing.