Colons are used when a second sentence begins with either a transitional phrase or conjunctive adjective (such as although, even so, accordingly, or moreover). They also help to separate items in a serial list that already includes commas.
However, the colon is one of the most misunderstood punctuation marks in English grammar. Using the wrong one can completely change the meaning of your sentence.
What is a Colon?
A colon is a punctuation mark that is used to connect sentences, highlight a word or phrase, and introduce lists, quotes, or explanations. It’s often confused with a semicolon, but it’s important to know when to use each punctuation mark correctly.
When using a colon, it is usually followed by a space, and it should never be followed by a hyphen or dash. In fact, it’s recommended that you avoid using a hyphen or dash if possible, as this can make your writing sound choppy and difficult to read.
A colon should always come AFTER an independent clause (or complete sentence) and BEFORE you rename or explain something that comes before it. That said, you can also choose whether or not to capitalize the first letter of any words that follow the colon if they would be considered their own clause in other circumstances—it’s just a matter of style. In math, the colon is sometimes used with a double colon to denote a tensor contraction involving two indices, and it’s commonly used with a single colon for ratios involving two numbers.
What is a Semicolon?
A semicolon is a punctuation mark used to separate independent clauses in specific situations. It can also be used as a stylistic tool to add a bit of flair to your writing. According to the Macquarie Dictionary, a semicolon creates a longer pause than a comma but is shorter than a full stop.
The most common use for a semicolon is to connect two independent clauses that are closely related in meaning. These clauses are able to be linked together by a coordinating conjunction (and, but, or, not, for, so, yet) if the connection between them is clear, but it is also possible to simply link the two sentences together using a semicolon.
The key to understanding the correct use of a semicolon is that each statement on either side of the punctuation mark should be able to stand as a complete sentence in its own right. You should be able to replace the semicolon with a period and it would still make sense.
How to Use a Colon
The colon is used between two independent clauses if the second sentence clarifies, explains, illustrates, or paraphrases the first. The two sentences must be complete, and their content should be closely related. This usage of the colon is especially helpful when writing a serial list or when using a phrase such as including, for example, or even:
It’s important to note that some style guides don’t recommend capitalizing the first word after a colon, though this isn’t always the case. A colon can be used after a salutation in a letter (To Whom It May Concern:) or between hours and minutes to indicate time (4:45:00 expresses four hours, forty-five minutes, and zero seconds). Also, many citation styles use a colon between a title and subtitle and between the publisher and date in bibliography entries. However, a colon should not be used after the expressions the, following, or as follows. These are not complete independent clauses and should be separated by a comma instead.
How to Use a Semicolon
As its name suggests, the semicolon is a punctuation mark that sits between a period and a comma. It connects independent clauses when a coordinating conjunction would be overly cumbersome. It is also used to separate items in a list that contains internal punctuation, such as commas and dashes.
However, the semicolon can’t be used as a stand-in for a question mark. It is only appropriate to use if it separates two closely related ideas that could function as their own sentence. For example, “I met John, Stacy, and Sally at the weekend retreat; but I didn’t meet Kathy.”
The semicolon is also an excellent choice to replace a comma when connecting independent clauses that begin with a conjunctive adverb or transitional expression. For example, “I visited several stunning locations during my trip; including Heidelberg; the Great Mosque (also known as the Mezquita) in Cordoba; and a quaint village in Undredal.”