Download this handout (PDF)


When people talk, they have many clues as to context, such as body language, eye contact, and inflection. We don’t have any of those things in writing, so we use punctuation instead.  Punctuation in conventional Western academia can sometimes be tricky; however, many professors and jobs will require proficiency.

Independent Clauses

Let’s start with a complete sentence, or independent clause:

The lemmings crowded together at the cliff’s edge.

The clause has a subject (lemmings) and a verb (crowded) and a complete idea; thus, it is independent.

Generally, an independent clause ends with a period:

They shoved at each other, grumbling and arguing.

Sometimes an independent clause ends in an exclamation point:

One of them fell over the edge!

Once you have one sentence written, you’ll need a few more, right?

Coordinating Conjunctions

You can vary your sentences and form a compound sentence by joining two sentences with a comma and a coordinating conjunction.


  1. To cause to work or function in a common action or effort.
  2. To make harmonious; harmonize.
  3. Grammar. To link (syntactic units) at an equal level. (American Heritage Dictionary)

You might have memorized the coordinating conjunctions in elementary school. FANBOYS provides a mnemonic for remembering them: for, and, nor, but, or, yet, so.

You should place one of the conjunctions between the two complete sentences, but you need a comma, too:

No one expected the accident, but they just couldn’t help peering over the edge to see what was happening.

Comma Splices

One very common error that people make is to use a comma instead of a period or a semicolon in between two complete sentences. Using just a comma creates a comma splice. A comma isn’t strong enough to hold the sentences together, so you need something stronger, such as a period or a semicolon.

(Just for the record, you create a fused sentence when you don’t use any punctuation or a conjunction between sentences, and a run-on sentence occurs when you use one of the coordinating conjunctions without a period.)


One mark of punctuation that can be incredibly effective is the semicolon, although people tend to shy away from it because they don’t know how to use it. A semicolon separates two complete sentences that are closely related and are basically equal in importance:

The lemming, Lorenzo, squealed all of the way down; he was sure he was breathing his last.

Conjunctive Adverbs

The semicolon can be put to even better use when incorporated with a conjunctive adverb. Don’t worry about figuring out what a conjunctive adverb is. Here is a list of them:

  • therefore                                
  • consequently                         
  • likewise
  • moreover                                
  • then                                        
  • still
  • also                            
  • otherwise                               
  • nevertheless
  • in fact                         
  • for example                            
  • furthermore
  • instead           

Don’t forget everyone’s favorite: however.

The words listed above can serve as sentence interrupters (explained below), but here we’ll talk about them as conjunctions (joining words) that tie two independent clauses together with a semicolon. Remember that a semicolon implies an equal level of importance; the conjunctive adverb strengthens the connection by suggestion how those two equally important sentences are related to each other.

The lemmings crowded even closer to the edge as Lorenzo’s squeals faded; in fact, they pushed so hard that Loretta fell, too!

Let’s try using the conjunctive adverbs as interrupters. In this case, you do not have two complete sentences; instead, you have one independent clause that is interrupted with the adverb:

Watching them fall, however, did not reduce the pushing.

When to Use Commas

We can use other interrupters, too, but whether or not you use commas depends upon whether the information is essential information or nonessential information.

Essential information should NOT be separated from the rest of the sentence with commas, as it will change the meaning of the sentence if it is removed:

The lemmings at the back of the crowd decided to run to the side of the cliff so that they’d get a better view.

If you were to take out the essential information, you’d change the meaning of the sentence:

The lemmings decided to run to the side of the cliff so that they’d get a better view.

No commas around essential information, then.

Nonessential information can be removed from a sentence without changing the basic meaning, so you do need to separate it with commas:

They ran around trees and over hummocks, squabbling all of the way, and reached the nearby scenic overlook in no time.

Taking out "squabbling all of the way" would not change the meaning; doing so would simply eliminate some additional details.

Sometimes these types of phrases can come at the end of the sentence as an afterthought. Generally, the information augments the sentence rather than being an essential part of it; therefore, you should include a comma:

They yelled at the other lemmings to alert them to the danger they were in, thinking they could actually be heard.

By now you have several ways of punctuating two sentences of equal importance. Now let’s look at ways of punctuating two sentences that are NOT of equal importance.

Subordinate Clasues and Conjunctions

Never underestimate the value of a subordinator. At work, you have a boss; therefore, you are a subordinate, meaning you must answer to the person who has power over you.

The same idea works for subordinating conjunctions. Oh, and conjunction is in there, so you are still joining two independent clauses. One of the sentences is more important than the other, though, so you need to subordinate the other one.

Here’s a list of subordinators:




as if

as long as







in order that


provided that


so that



















Subordinators can come at the beginning of the first complete sentence or at the beginning of the second complete sentence. Add it to whichever sentence is less important.

The tricky part is where to place the comma. Where to place the comma might be determined by where YOU are. In the United States, place the comma after the first independent clause if that is the one being subordinated:

Since Loretta’s mother was the sensitive type, the others brought her a drink of water.

Notice that the word since appears at the beginning of the first sentence, transforming it from an independent to a subordinate clause. Also, a comma now separates the subordinate clause from the independent clause.

If we want the second complete sentence to be subordinated, then we don’t use a comma:

The First Responders relaxed once Loretta’s mother was resting comfortably.

If you are in England, you probably have to reverse those guidelines: no comma when the subordinate clause comes first, comma when the subordinate clause comes second:

Since Loretta’s mother was the sensitive type the others brought her a drink of water.

The others brought Loretta’s mother a drink of water, since she was the sensitive type.

We can’t leave Lorenzo and Loretta suspended in mid-air, so let’s try some subordinate clauses to rescue them:

Although Lorenzo continued to scream as he descended, he abruptly stopped when he fell into a patch of thick, sweet clover.

Loretta hadn’t uttered a sound after she fell over the cliff.

When she landed on top of Lorenzo, she let out a surprised “Oooof.”

Lorenzo and Loretta threw their arms around each other once they realized they were safe.

Safe and sound. We have a few more bits of information about commas and punctuation for you, but first let’s talk about colons.

You use a colon after a complete sentence when you are introducing a list or providing specific details about something. Separate the items in the series with a comma; if you have a series of clauses instead, then use semicolons to separate the each part in the series:

  • Lorenzo and Loretta were overcome with emotions: gratitude, happiness, and a bit of euphoria.
  • Loretta’s mother couldn’t decide how she felt: angry with her daughter, grateful to Lorenzo, or perturbed that no one was paying attention to her.
  • The lemmings watching from above reached a few conclusions: Lorenzo and Loretta were all right; thick, sweet clover was much softer than they figured; they probably shouldn’t crowd together at the edge of a cliff.

Here are the promised bits of information: When you are writing a research paper and you include block quotations, you should use a colon and a complete sentence to introduce the quotation:

In Lawrence Wright’s 2013 history of Scientology, Going Clear, he profiles former church member Paul Haggis, describing a pivotal moment in Haggis’ childhood that made him vulnerable to the religion’s self-improvement strategies:

When Paul was about thirteen, he was taken to say farewell to his grandfather on his deathbed. The old man had been a janitor in a bowling alley, having fled England because of some mysterious scandal. He seemed to recognize a similar dangerous quality in Paul. His parting words to him were, “I’ve wasted my life. Don’t waste yours.” (15)

When you have three or more items in a series, the final comma is optional. (Including the comma is referred to as a serial comma or an Oxford comma.) Let your level of formality decide whether or not to use the final comma, but be consistent.

Now you know a lot of stuff about punctuation. As always, if you’re not sure about something, please check with us in the MAX Center, check out a writing manual, or go to the OWL.