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Punctuation on ACT English: Apostrophes, Colons, and More


What's the difference between a period and a semicolon? Between a comma and a dash? These questions bedevil not just students, but even professional writers. Punctuation can be one of the weirdest, most confusing parts of writing.

However, the ACT English section isn't writing—it's a multiple choice test, which means that every question has to have only one correct answer. The ACT tests a specific set of punctuation rules, most of which deal with commas. I ;covered commas in a separate post—here I'll be explaining the other punctuation rules you need to know, which deal with apostrophes, semicolons, colons, and dashes.

Here's brief rundown of everything this article will cover:

  • Using apostrophes in possessives and contractions
  • Understanding the differences between semicolons, colons, and dashes
  • Answering ACT English questions on punctuation
  • ACT English practice questions


Feature Image Credit: xlibber, used under CC BY 2.0


Apostrophes: Possessives and Contractions

Apostrophes on the ACT can be really tricky. You may assume you know the rules, but the ACT tests these concepts in its own weird way. As such, I'm going to briefly review the relevant rules, and then go over in detail how these concepts are tested on the ACT and what the common errors that you need to watch out for are.



The basic rules for forming possessives are quite simple.

If a word is singular or if it's plural but doesn't end in "s," then you add "'s" to the end of the word.

the fox → the fox’s

the women → the women’s

To create a possessive for a plural word that does end in "s," you simply place an apostrophe at the end of the word, after the "s."

the archaeologists → the archaeologists

Let's look at how this works in a sentence:

At the tinkers convention, Jose browsed for a long time before deciding he wanted to buy something from the leather workers stall.

Clearly, this sentence is missing a number of apostrophes. The convention is for a lot of tinkers, so there should be an apostrophe after the s. It's probably just one leather worker at the stall though, so the apostrophe should go before the s.

At the tinkers' convention, Jose browsed for a long time before deciding he wanted to buy something from the leather worker's stall.

On the ACT English, possessives questions aren't so much about knowing the rules as they are about determining whether you need an apostrophe at all and, if so, whether the noun is meant to be plural or singular.


Should This Noun be Possessive?

Happily, there's an easy trick to determine whether a noun should be possessive. "Sally's ball" is just another way of saying "the ball of Sally." So if you want to figure out whether a noun is meant to be possessive, take the noun, put an "of" in front of it, and stick it after the noun or phrase that follows it. This may sound complicated, but it's actually very easy. 

Let's walk through an example.

When my computer crashed, I lost a months work on my plan to take over the world.

Should month be possessive? Try switching it around:

When my computer crashed, I lost the work of a month on my plan to take over the world.

That makes sense: the point is that I lost all the work I did in a month. The correct version of the sentence is:

When my computer crashed, I lost a month's work on my plan to take over the world.

It's easy to assume that because a month isn't a person it can't be possessive, but that's not the case. Any noun can be possessive.

In general, when dealing with possessive nouns, you're more likely to see questions where there's a necessary apostrophe missing (or misplaced, which we'll discuss shortly), than you are to see ones with extra apostrophes that you don't actually need.


 Is the Noun Meant to be Plural or Singular?

The other factor you'll need to consider when placing apostrophes is whether the possessive noun is meant to be singular or plural. Whether "the neighbor's dog" or "the neighbors' dog" is correct is dependent on whether there is only one neighbor or more than one. When working on ACT English questions, you'll need to look at context clues to determine how many of the noun there are meant to be.

Let's revisit our example from above:

When my computer crashed, I lost a months work on my plan to take over the world.

We've already established that "months" should be possessive. But how do we know that it's "month's" not "months'"? The singular article "a" gives us the clue—"a months" makes no sense, so the noun has to be singular.

Consider a slightly different version of the sentence:

 When my computer crashed, I lost some months work on my plan to take over the world.

"Some" indicates more than one. So when we make "months" possessive, we need to put the apostrophe after the "s":

 When my computer crashed, I lost some months' work on my plan to take over the world.

Keep in mind that the relevant context clues may sometimes be trickier to spot, so check the sentences before and after the underlined one if you're unsure. 


ACT Example

The ACT tests possessives in almost exactly the same way we just discussed. Take a look at this example from an official ACT English section:


Let's go through our two questions in order.

Should "family" be possessive? If we switch around the word order to "the farm of his family" that makes sense, so yes, the noun should be possessive. (In this example, you might also say "family farm" but you'll notice that isn't an answer choice.)

Is it "family" or "families"? First, think about what clues you can use—"his" is a good one. We're talking about Banneker's family specifically, and people generally only have one family. The singular form is correct. 

Now we know that we need an answer with "family" and an apostrophe, which narrows it down to A and B. We need to pick the one that correctly places the apostrophe before the "s" (since we're dealing with a singular noun), which is B.


body_apostrophe.jpgWhoever wrote this sign didn't know the correct rules for apostrophes (©Leo Reynolds)



When working with contractions, you only really need to know one rule: the apostrophe replaces the missing letter or letters.

Do not → don't (apostrophe replaces the second "o")

They have → they've (apostrophe replaces the "ha")

There are a few weird cases like "won't," but you don't need to worry about them. In fact, the ACT English generally doesn't ask about spelling of contractions. Why are we going over this rule then? Because there are a couple of very common contraction-related errors that the ACT English does test. 


Could Of vs. Could've

If you've done any ACT English practice you may have seen the construction "could of," "should of," or "would of." For example:

I should of gone to bed early, but I stayed up to play video games instead.

This sentence sounds fine if you read it aloud, but it's actually incorrect. I'm trying to say that I should have gone to bed—the correct spelling is "should've" not "should of":

I should've gone to bed early, but I stayed up to play video games instead.

Should of, could of, and would of are always wrong. If you're trying to determine if a contraction is correct in general, though, replace it with the fully written out form. This technique will come in handy with our next category of errors as well.



One of the most common mistakes students make on the ACT English is mixing up "it's," "its'," and "its." Do you know the difference?

  • It's — it is or it has
  • Its — possessive form of it
  • Its' — not a word

Think about it this way: a contraction must have an apostrophe to replace the dropped letters while no other pronoun possessives (his, her, my) have apostrophes. Its', meanwhile, is just a weird construction that only shows up on the ACT—it is never correct.

To summarize: for pronouns, an apostrophe ALWAYS indicates a contraction.

Though they're less common, errors with they're, there, and their and errors with who's and whose may also appear on the test. For more details on those, take a look at our post on word choice


Semicolons, Colons, and Dashes: Connecting Clauses and Phrases

We've covered apostrophes (above) and commas (elsewhere)—that leaves only three more punctuation marks: semicolons, colons, and dashes. Like commas, which they're often tested in conjunction with, these punctuation marks help clarify the relationships between clauses and phrases. Also like commas, you are far more likely to make an error by adding an unnecessary punctuation mark than by removing a necessary one, so err on the side of less punctuation.

We're going to go over the exact uses for each of these punctuation marks, but, first a quick disclaimer. Semicolons, colons, and dashes are almost always tested with commas or in the context of sentence fragments and sentence structure. We have separate posts on each of those, so make sure to look at them as well.



Semicolons are basically wishy-washy periods (or so their detractors claim); they connect two independent clauses. That previous sentence is an example! A semicolon is only correct if it could be replaced with a period. 

Incorrect: After seeing that the amusement park had four roller coasters; Maria was determined to ride them all.

Correct: The amusement park has four roller coasters; Maria was determined to ride them all.

In the first version of the sentence, a semicolon is being used incorrectly in place of a comma to connect a dependent and an independent clause. In the second version, it is correctly placed between two independent clauses.

Remember that semicolons are interchangeable with periods—this means that you will never be asked to choose between them. If the only difference between two answers is that one has a period and the other semicolon in the same spot, both answers must be wrong.

There is one other, much less common, use of semicolons: to separate items in a list, especially if they include commas. For example:

My whole family was at the reunion, including my cousins, Kirsten and Jeremy; my aunts, Tracy and Megan; and my grandparents, Carl and Jen. 

Again, there's a small chance you'll see this usage on the test, but it's very small. Don't worry about it too much.


body_semicolon.jpgMake sure to keep your semicolons happy by only using them between independent clauses! (©Mauricio Balvanera) 



Colons are easy to mix up with semicolons because the two punctuation marks look similar and have similar names. Colons can, in fact, connect two independent clauses, but they are usually used to introduce lists or explanations (you may have noticed that I tend to employ them for the latter purpose quite a lot). 

The key rule for colons is that they must come after a complete sentence. You should be able to put a period at the end of the clause before the colon and have it make sense. Otherwise, it doesn't matter if you're introducing a list or explanation, it's still wrong.

Incorrect: Liz went to the costume shop for the supplies she needed for Halloween, including: fake blood, plastic spiders, and a witch’s hat.

Correct: Liz went to the costume shop for the supplies she needed for Halloween: fake blood, plastic spiders, and a witch’s hat.

Correct: Liz went to the costume shop for the supplies she needed for Halloween: a holiday when people dress up in scary costumes and eat a lot of candy.

Correct: Liz went to the costume shop for the supplies she needed for Halloween: she was planning to dress up as a zombie witch.

The first sentence is incorrect, because the part that comes before the colon isn't a complete thought; "Liz went to the costume shop for the supplies she needed for Halloween, including" makes no sense on its own. The other three versions all correctly locate a colon at the end of the independent clause, "Liz went to the costume shop for the supplies she needed for Halloween."

You may have noticed that semicolons, colons, and periods can all be used between independent clauses. However, as I mentioned in regard to semicolons, you will never be asked to choose between the three—the distinctions are purely stylistic. If you have more questions on this topic, read our guide to sentence fragments and run-ons



Dashes are a strange and flexible punctuation mark—personally, they're my favorite! However, for the sake of the ACT English, you really only need to understand two of its uses: marking off a non-essential clause or phrase (just like a comma) and introducing a list or explanation (just like a colon).

Non-essential clauses and phrases provide extra information that can be removed without altering the meaning of the sentence. When dashes are used with non-essential clauses or phrases, the key is making sure that you don't mix them with commas. Both are equally correct, but you have to stick to one or the other.

Incorrect: Allie was minding her own business when her brother, a mischievous eight-year-old—snuck up and surprised her.

Correct: Allie was minding her own business when her brother—a mischievous eight-year-old—snuck up and surprised her.

Correct: Allie was minding her own business when her brother, a mischievous eight-year-old, snuck up and surprised her.

To mark off non-essential clauses is by far the most likely way you'll see dashes tested on the ACT English. However, you may also see dashes used to introduce a list or explanation, like so:

Allie’s eight-year-old brother surprised her—he snuck up behind her and yelled “boo!”

Dashes are relatively rare on the ACT, so just understand roughly how they can be used and you'll be fine.


ACT Example

As I mentioned above, these punctuation marks are often tested together. You can see what that looks like in this official ACT question:


On questions like this one, it's often easier to determine what doesn't work than what does.  So let's start with the semicolon; "but versatile boat" definitely isn't an independent clause, so we know a semicolon can't be correct. This construction also isn't a non-essential phrase (if you take it out the sentence no longer makes sense), a list, or an explanation, so we can rule out the dash. 

The comma is tempting because it's right before the coordinating conjunction "but," but it's actually incorrect. Think about what commas, dashes, colons, and semicolons are all meant to do: clarify relationships between clauses and phrases. That means you generally shouldn't stick them in the middle of a thought. "simple but versatile boat" is one idea, so you don't want to interrupt it with unneccesary punctuation. B is the correct answer.

Remember to always consider whether you really need a punctuation mark—you often don't.


body_rules-1.jpgBreaking the rules is great sometimes, but not on the ACT. (©Edward SImpson)


Applying Punctuation Rules on the ACT English

We've covered a lot of rules and strategies for answering punctuation questions on the ACT English. I've rounded up the key points below, so that you can see the key rules to remember and best strategies to implement!


Key Rules for Punctuation:

  • Possessives: the apostrophe goes before the s for singular nouns and plural nouns that don't end in s and after the s for plural nouns that do end in s
  • Contractions: the apostrophe replaces the missing letters
  • Possessive pronouns don't have apostrophes
  • Semicolons connect two complete sentences
  • Colons come after a complete sentence and introduce a list or explanation
  • Dashes mark off non-essential clauses or introduce lists and explanations


Helpful ACT English Strategies:

  • Use "of" to check whether a noun should be possessive
  • Use context clues to determine whether a possessive noun is plural or singular
  • Remember that non-person nouns can be possessive
  • Answer choices that are always wrong: should of, could of, would of, its'
  • You'll never be asked to choose between interchangeable punctuation marks: either you're missing something or both answers are wrong
  • Make sure the punctuation marks around a non-essential clause or phrase are always the same: either a pair of commas or a pair of dashes, never one of each 
  • Since there are a variety of different punctuation marks that serve similar purposes, use process of elimination to rule out the ones that can't be right, rather than trying to figure out what you think it should be
  • If one choice doesn't have a punctuation mark at all, be sure to give it careful consideration—it will often be the correct answer
  • Make sure to study the related topics of commas and run-on sentences as well


Put Your Skills into Action!

The best way to improve on the ACT English is to practice. To that end, I've created some sample ACT style questions where you can test out your new knowledge.


1. The two main types of camels are; bactrian camels, which have two humps, and dromedary camels, which have one.


B. are: bactrian

C. are bactrian

D. are, bactrian


2. Tootsie Pops are beloved for the lollipops chocolatey centers, even though no one knows how many licks it takes to get to them.


G. lollipops'

H. lollipop's

J. lollipop


3. Adding to the drama, Joe according to the rumor mill — stole Alfonso's girlfriend.


B. Joe,

C. Joe who

D. Joe —


4. Even though she's been trying to cut it down, Fran's action album collection is still impressive: over 400 vinyl records, 2000 CDs, and even a handful of tapes.


G. impressive; over

H. impressive over

J. impressive, it's


Answers: 1. C, 2. G, 3. D, 4. F


What's Next?

Make sure you also understand the comma rules on the ACT English. Commas are often tested in conjunction with other forms of punctuation.

Not sure what else you need to study? Check out our guide to the most commonly tested ACT grammar rules.

Start thinking big picture! Learn the 5 key concepts you need to ace the ACT English and the 9 steps to a 36 (as tested by a perfect scorer).



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Alex Heimbach
About the Author

Alex is an experienced tutor and writer. Over the past five years, she has worked with almost a hundred students and written about pop culture for a wide range of publications. She graduated with honors from University of Chicago, receiving a BA in English and Anthropology, and then went on to earn an MA at NYU in Cultural Reporting and Criticism. In high school, she was a National Merit Scholar, took 12 AP tests and scored 99 percentile scores on the SAT and ACT.

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