When to Use a Semicolon vs Colon, Comma, and Em Dash (; : , —)

Punctuation rules should generally be followed in academic writing. Putting a comma between two independent clauses will confuse your readers and make your work frustrating to read. On the other hand, using a semicolon correctly can add nuance and subtlety to any kind of writing.

But what is a semicolon? How do colons and dashes work? How do you use a comma correctly?
This article provides some useful tips for using semicolons (;), colons (:), commas (,) and dashes (—).

When to Use Semicolons (;)

A semicolon is used to separate two ideas (two independent clauses) that are closely related. They can also be used when listing complex ideas or phrases that use commas within them.  Essentially, a semicolon is like a comma with more meaning or a colon with more flexibility. Knowing how to use semicolons properly will make your writing more sophisticated and subtle.

Using semicolons to join two or more ideas in a sentence

The universe has always called to human beings; there could be no more final frontier than space.

Using semicolons to join two independent clauses

Sam thought David was inviting him to the picnic to enjoy a nice day out; as it turned out, David was planning a surprise birthday party.

Using semicolons to present items in a list or series with commas or long items

Our family members came all the way from Denver, Colorado; Rochester, Minnesota; and even Paris, France.

Using semicolons to connect independent clauses joined by a coordinating conjunction

My main research objective is to isolate the cause of the disease, as well as to contribute to the existing literature; for this will bring an end to starvation across the continent, create new study designs related to epidemiology, and change the very paradigm of my research field.

More Tips on How to Use Semicolons (;)

Use a semicolon between independent clauses linked with a transitional expression

Transitional expressions are often separated by a semicolon as well. These include conjunctive adverbs and transitional phrases such as those in the tables below.

Using a Semicolon vs Comma vs Colon (; , 🙂

*The conjunctive adverb “however” shows a connection between the two independent clauses; do not use a comma to connect two independent clauses without a coordinating conjunction (and, but, or, nor, etc.).

*Using only commas, it is unclear what items are being listed exactly. Semicolons help divide listed items that each contain commas.

When to Use a Colon (:)

A colon is used to make lists and tell the reader, “This is what I mean.” The colon should not be used often in most kinds of writing unless there are extensive lists involved. The rules of the colon are strict but fairly easy to remember. Knowing how to use a colon comes in handy when making lists or introducing subordinate information or details.

Using colons to introduce an item or series

Humans use five major senses: sight, hearing, smell, taste, and touch.

Using colons to separate independent clauses to illustrate, explain, paraphrase, or expand an idea

Martha realized that her worst fear was coming true: her son was being sent to war.

*The information after the colon explains Martha’s fear in the form of an independent clause.

Using colons to follow the salutation in a formal letter

To the Central Valley Committee Chairman:

More Tips on How to Use Colons (:)

Do not capitalize the first word after the colon unless it is a proper noun, is part of a quote, or is the first in a series of sentences:

When a quotation contains multiple sentences, introduce it with a colon rather than a comma

In Chapter 3, the author explains his theory: “Dogs have dreams, but they don’t dream as humans do. Their dreams reflect a primal desire for pleasure, whereas humans are preoccupied with the ego and self-image. This is equally true in wakefulness and sleep.”

A complete sentence after the colon is not necessary—a word or phrase is fine.

There is one mantra that can sum up our position on climate change: urgent action.

Common Colon Mistakes (:)

Separating two clauses that have equal rank or unrelated information

(*Use a period if the clauses are not at all related. Use a semicolon if the information in the second clause is somewhat related but does not illustrate, explain, or paraphrase the first clause.)

Overusing the colon

The colon is a powerful punctuation mark and should be used sparingly. Think of it as a stop sign that calls readers’ attention and says, “Hey! Pay attention to this. This is important.” If there are too many stop signs on a street, you won’t be able to drive very smoothly or quickly. This is the same effect colons can have on readers.

Because colons are so attention-grabbing, they can clearly indicate which information is important. For this reason, many authors use colons to introduce their main argument or supporting evidence.

When to Use a Comma (,)

Commas are the most frequently used (and abused) punctuation mark in most kinds of writing. The reason for this is that they have so many uses and so many rules—it can be hard to keep track of them all. Let’s take a look at just a few of the comma’s crucial functions and discuss when to choose a comma over another similar punctuation mark.

Using commas to list items or short phrases

I bought bread, cheese, and pickles at the grocery store.

Using commas to separate long independent clauses connected by conjunctions

Astronomers have known about the positions of stars for centuries, but they didn’t understand that the earth revolves around the sun.

Commas after an introductory phrase

In preparation for the next convention, the representatives studied up on the most important issues.

Using commas to separate a parenthetical phrase or interrupter

All doctors, if they care about their patients, are concerned with good office hygiene.

Common Comma Mistakes (,)

Comma splices

A comma splice is a comma mistake that involves using a comma to join two independent clauses together. Do NOT use a comma to divide two independent clauses without a conjunction.

Combining lengthy phrases

Using commas with compound sentences or to separate clauses with other commas can cause confusion (use a semicolon instead).

When to Use an Em Dash (or Dashes) (—)

The dash (or, more specifically, the “em dash”) is perhaps the most versatile of the punctuation marks. However, like the semicolon, it is underutilized in most kinds of writing. It can function as a comma, parentheses, or colon, but creates subtly different effects in each case.

Using an em dash in place of a comma

Em dashes can be used in pairs to replace commas when writing a parenthetical or interruptive phrase. The dashes have a slightly more emphatic feel, making the reader focus on the information that is set inside the special marks.

The dashes emphasize that the baby was premature, identifying it is an important detail in this sentence.

Using em dashes instead of parentheses

Put a pair of em dashes in the same position in which you would use parentheses. Since they are less formal, fewer dashes than parentheses are found in academic writing. However, they do cause more of an obvious interruption and therefore more emphasis. They can also be used as a sort of “meta” parentheses when the content between the dashes already contains parentheses.

When dashes replace parentheses, the surrounding punctuation is omitted:

*Em dashes are more visible than parentheses and therefore interrupt the flow of the sentence a bit more and draw attention to the content.

When used instead of parentheses at the end of a sentence, only a single em dash is used:

*The dash works especially well when placed at the end of a sentence—it extends the sentence like an addendum, allowing a wide range of new information to be added..

Using an em dash instead of a colon

Use an em dash instead of a colon when you want to emphasize the conclusion of your sentence without giving it all of the connotations that a colon brings. A dash can add “extra” information and is more flexible in this way. It is also less formal than a colon.

*Using the dash instead of a colon conveys a sense of anticipation (or of inevitability) and can add an almost editorial feel to the writing.

Choose Punctuation with Context and Audience in Mind

As with any technical decisions regarding writing, when choosing which punctuation marks to use and apply consistently, it is a good idea to consider your audience and the context of your work. For instance, researchers looking to publish in journals should read articles from the journals they are targeting to see which punctuation marks are used by most authors in that journal. The same rule applies to any newspaper, magazine, or periodical for which your writing is intended.

Proofread to Ensure Proper Punctuation

Although you hopefully have learned a bit more about how to use these punctuation marks appropriately, receiving editing and proofreading services before finalizing your document ensures that your paper is completely free of errors in grammar, punctuation, mechanics, and style issues. See our proofreading prices page for a full menu of our editing services and rates.