Punctuation shows you how to read and understand sentences. For instance, the period at the end of the last sentence indicated that the sentence had come to an end and that the next sentence would begin a new thought. We could go on and on like this, but you get the point.
The ACT English Test requires that you know the rules for the following types of punctuation:
  1. Commas
  2. Apostrophes
  3. Semicolons
  4. Colons
  5. Parentheses and Dashes
  6. Periods, Question Marks, and Exclamation Points
Not all of these punctuation types are tested on every English Test. However, you can definitely expect to find questions dealing with the first four items of the list on the English Test you take.
Misplaced, misused, and missing commas are the most frequent punctuation offenders on the English Test. Commas can serve several functions within sentences:
Commas Separate Independent Clauses Joined by a Conjunction
An independent clause contains a subject and a verb (an independent clause can be as short as “I am” or “he read”), and it can function as a sentence on its own. When you see a conjunction (and, but, for, or, nor, yet) joining independent clauses, a comma should precede the conjunction. For example,

An independent clause contains a subject and a verb, and it can function as a sentence on its own.

Lesley wanted to sit outside, but it was raining.

Henry could tie the shoe himself, or he could ask Amanda to tie his shoe.

In each example, the clauses on both sides of the comma could stand as sentences on their own. With the addition of the comma and conjunction, the two independent clauses become one sentence.
Commas Delineate a Series of Items
A series contains three or more items separated by commas. The items in a series can be either nouns (such as “dog”) or verb phrases (such as “get in the car”). Commas are essentially the structural backbone of a series. For example,

The hungry girl devoured a chicken, two pounds of pasta, and a chocolate cake.

When he learned his girlfriend was coming over, Nathaniel took a shower, brushed his teeth, and cleaned his room.

The comma follows all but the last item in the series. When using a conjunction, such as “and” or “or,” at the end of the series, remember to precede it with a comma (“. . . brushed his teeth, and cleaned his room”).
Commas Separate Multiple Nonessential Adjectives Modifying a Noun
When two or more nonessential adjectives modify a noun, they should be separated by a comma. Of course, the key to figuring out whether there should be a comma separating two adjectives is being able to determine whether the adjectives are essential or nonessential. Luckily, there’s a simple rule that can help you: the order of nonessential adjectives is interchangeable. For example,

Rebecca’s new dog has long, silky hair.

The loud, angry protesters mobbed the building.

These two sentences would make equal sense if you switched the order of the adjectives: “Rebecca’s new dog has silky, long hair” and “The angry, loud protesters mobbed the building.”
The case is different if you have an essential adjective modifying the noun. Essential adjectives specify the nouns they modify; they are bound to the noun, so that the noun loses meaning if separated from its adjective. A noun modified by an essential adjective should be treated as a single noun. If you come across two adjectives modifying a noun, and one is essential, you should not use a comma between them. For example,

My mother hates noisy electronic music.

“Electronic music” functions as an indivisible noun; “electronic” specifies the type of music the mother hates. “Noisy” is a nonessential adjective modifying the noun “electronic music.” Changing the order of “noisy” and “electronic” (“My mother hates electronic noisy music”) would not make sense. If you can’t change the order of two adjectives preceding a noun, you know the adjective nearest the noun is essential, so you should not use a comma.
Commas Set Off Dependent Phrases and Clauses from the Main Clause of a Sentence
Unlike independent clauses, dependent phrases and clauses are not sentences in themselves; rather, they serve to explain or embellish the main clause of a sentence. When they appear at the beginning of a sentence, they should be set off from the main clause by a comma. For example,

Scared of monsters, Tina always checked under her bed before going to sleep.

After preparing an elaborate meal for herself, Anne was too tired to eat.

The first example shows a dependent clause (“Scared of monsters”) acting as an adjective modifying “Tina.” The second example shows a dependent clause acting as an adverb. Since the adverbial clause is at the beginning of the sentence, it needs to be set off from the main clause by a comma. Adverbial clauses should also be set off by commas if they appear in the middle of a sentence. However, if an adverbial clause appears at the end of a sentence, you do not need to use a comma. For example,

Anne was too tired to eat after preparing an elaborate meal for herself.

Commas Set Off Nonessential Phrases and Clauses
Nonessential phrases are like nonessential adjectives in that they embellish nouns without specifying them. Nonessential phrases should be set off from the rest of the sentence by commas. For example,

Everyone voted Carrie, who is the most popular girl in our class, prom queen.

The decrepit street sign, which had stood in our town since 1799, finally fell down.

When you use nonessential phrases like the two above, you assume that “Carrie” and “the decrepit street sign” do not need any further identification. If you remove the nonessential phrases, you should still be able to understand the sentences.
Restrictive phrases, on the other hand, are not set off by commas because they are necessary to understand the modified noun and the sentence as a whole. For example,

The girl who is sick missed three days of school.

The dog that ate the rotten steak fell down and died.

If you removed the restrictive phrases (“who is sick” and “that ate the rotten steak”) from these sentences, you would be left wondering “which girl?” and “which dog?” These restrictive phrases are used to identify exactly which girl missed school and exactly which dog died. Setting off “who is sick” in commas would assume that the girl’s identity is never in doubt; there is only one girl who possibly could have missed school. In this case, we know the identity of the girl only because the restrictive phrase specifies “the girl who is sick.”
Commas Set Off Appositives
Appositives are similar to nonessential phrases. An appositive is a phrase that renames or restates the modified noun, usually enhancing it with additional information. For example,

Everyone voted Carrie, the most popular girl in school, prom queen.

The dog, a Yorkshire Terrier, barked at all the neighbors.

In these two examples, “the most popular girl in school” and “a Yorkshire Terrier” are appositives used to explain the nouns they modify. You should be able to draw an imaginary equal sign between the noun and the appositive modifying it: Carrie = the most popular girl in school, the dog = a Yorkshire Terrier. Because they are equal, you should be able to swap them and retain the meaning of the sentence: “Everyone voted the most popular girl in school, Carrie, prom queen.”
Apostrophes are the second most commonly tested punctuation mark on the English Test. Apostrophes primarily indicate possession, but they also take the place of omitted letters in contractions (for example, “was not” becomes “wasn’t” and “it is” becomes “it’s”). You will be tested chiefly on your knowledge of the apostrophe’s possessive function.
The Possessive and Singular Nouns
A singular noun (for example: Simon, the dog, the bottle) can be made possessive by adding an apostrophe followed by an “s”. For example,

Simon’s teacher was in the room.

My mom forgot the dog’s food.

We removed the bottle’s label.

The apostrophe follows directly after the noun. If you move the apostrophe after the “s” (for example, if you write “dogs’” rather than “dog’s”), you will change the meaning of the sentence (see “The Possessive and Plural Nouns” below). If you forget the apostrophe altogether, you will render the sentence meaningless.
The Possessive and Plural Nouns
Most plural nouns (for example: the boys, the dogs, the bottles) can be made possessive by adding only an apostrophe. For example,

The boys’ teacher was in the room.

My mom forgot the dogs’ food.

We removed the bottles’ labels.

The apostrophe directly follows plural nouns that end in “s” to make them possessive.
But for plural nouns that do not end in “s” (for example, “women”), you should treat the plural form as a singular noun (i.e., add an apostrophe followed by an “s”). For example,

The women’s locker room needs to be cleaned.

The Possessive and Multiple Nouns
Sometimes you’ll want to indicate the possessive of more than one noun (Nick and Nora, Dan and Johann). The placement of the apostrophe depends on whether the possessors share the possession. For example,

Nick and Nora’s dog solves crimes.

Dan’s and Johann’s socks are dirty.

In the example of Nick and Nora, the dog belongs to both of them, so you treat “Nick and Nora” as a single unit, followed by a single apostrophe and “s.” In the second example, both Dan and Johann have dirty socks, but they don’t share the same dirty socks, so you treat Dan and Johann as separate units, giving each an apostrophe and “s.”
The Possessive and Pronouns
Unlike nouns and proper nouns, the possessive case of pronouns does not use an apostrophe. The following chart gives you nominative pronouns (the ones you use as subjects) and the corresponding possessive pronouns:
Nominative Pronoun Possessive Pronoun
I my
you (s.) your
she her
he his
we our
you (pl.) your
they their
it its
who whose
For example,

The dog chewed on its tail.

You should give him your wallet.

Don’t confuse the “its” and the “your” above with “it’s” and “you’re.” This mistake is frequently tested on the English Test (see below).
Its/It’s, Their/They’re
The ACT will test you on your ability to distinguish between “its” and “it’s.” “Its” is the possessive form of “it.” “It’s” is the contraction of “it is.” This can be tricky to remember, since you are normally trained to associate apostrophes with possession. But when you’re dealing with “its” versus “it’s,” the apostrophe signals a contraction. The same is true for “their/they’re/there,” “your/you’re,” and “whose/who’s.” Make sure you are aware of these exceptions to the apostrophe rule of possession.
Try the following practice problem:
 Your face  is red.
B. You’re face
C. Your nose
D. OMIT the underlined portion.
You can eliminate choices C and D immediately: C changes the meaning of the sentence for no particular reason, and D leaves you without a complete sentence. The decision comes down to “Your” and “You’re.” If you don’t know the correct answer, try replacing “You’re” with “You are.” The resulting sentence is “You are face is red”—an odd remark. The correct answer is A, “NO CHANGE.” You can employ this replacement technique whenever you don’t know the answer to a possessive-or-contraction question. Once you replace the contraction with the full phrase, your ear will tell you which choice is right.
You’ll usually find several questions dealing with semicolons on the English Test. The main functions of a semicolon that you should know for the English Test are its ability to join related independent clauses and its use in a series.
The Semicolon and Two Independent Clauses
Semicolons are commonly used to separate two related but independent clauses. For example,

Julie ate five brownies; Eileen ate seven.

Josh needed to buy peas; he ran to the market.

In these cases, the semicolon functions as a “weak period.” It suggests a short pause before moving on to a related thought, whereas a period suggests a full stop before moving on to a less-related thought. Generally, a period between these independent clauses would work just as well as a semicolon, so the ACT won’t offer you a choice between period or semicolon on the English Test. But you may see the semicolon employed as a weak period in an answer choice; in that case, you should know that it is being used correctly.
Frequently, you will see two independent clauses joined by a semicolon and a transitional adverb (such as consequently, however, furthermore, indeed, moreover, nevertheless, therefore, and thus). For example,

Julie ate five brownies; however, Eileen ate seven.

Josh needed to buy peas; thus he ran to the market.

These sentences function similarly to those joined by a comma and a conjunction. Here, the semicolon replaces the comma, and the transitional adverb replaces the conjunction. Most transitional adverbs should be followed by a comma, but for short adverbs such as “thus,” the comma should be omitted.
The Semicolon and the Series: When the Comma’s Already Taken
The semicolon replaces the comma as the structural backbone of a series if the items already contain commas. For example,

The tennis tournament featured the surprise comeback player, Koch, who dropped out last year due to injuries; the up-and-coming star Popp, who dominated the junior tour; and the current favorite, Farrington, who won five of the last six tournaments.

If you used commas rather than semicolons in the above sentence, anyone reading the sentence would feel pretty confused. The semicolons in this example function exactly as commas do in a series, but they allow you to avoid overpopulating the sentence with commas.
You’ll probably be tested on your knowledge of colons a couple of times on the English Test. The ACT writers want to be sure that you know how colons introduce lists, explanations, and quotations.
The Colon and Expectation
Colons are used after complete sentences to introduce related information that usually comes in the form of a list, an explanation, or a quotation. When you see a colon, you should know to expect elaborating information. For example,

The wedding had all the elements to make it a classic: the elegant bride, the weeping mother, and the fainting bridesmaids.

In this example, the colon is used to introduce a list of classic wedding elements. Without the list following the colon, the sentence can stand alone (“The wedding had all the elements to make it a classic”). By naming the classic elements of a wedding, the list serves mainly to explain and expand upon the independent sentence that precedes it.
Check out this example of another way to use colons:

The wedding had all the elements to make it a classic: the elegant bride beamed as her mother wept and as the bridesmaids fainted.

Here, the clause following the colon also has an explanatory function. In this case, the colon joins two independent clauses, but the clause following the colon is used to explain and expand the first.
Colons can also be used to introduce quotations. For example,

The mother’s exclamation best summed up the wedding: “If only the bridesmaids hadn’t fainted!”

Here, the colon is used to introduce the mother’s exclamation. Make sure the quotation following the colon is related to the sentence.
Colon Problems
You should learn the following rules in order to avoid erroneous colon use on the English Test:
A Colon Should Always Be Preceded by an Independent Clause.

WRONG: The ingredients I need to make a cake: flour, butter, sugar, and icing.

RIGHT: I need several ingredients to make a cake: flour, butter, sugar, and icing.

In the “WRONG” example, a sentence fragment precedes the list of items. The sentence should be reworked to create an independent clause before the colon.
There Should Never Be More Than One Colon in a Sentence.

WRONG: He brought many items on the camping trip: a tent, a sleeping bag, a full cooking set, warm clothes, and several pairs of shoes: sneakers, boots, and sandals.

RIGHT: He brought many items on the camping trip: a tent, a sleeping bag, a full cooking set, warm clothes, sneakers, boots, and sandals.

If you see a sentence that contains more than one colon, the sentence needs to be rephrased. Lists within lists or explanations within explanations do not work in standard written English.
Other ACT Punctuation
The English Test rarely tests punctuation marks other than the ones listed above. But in the odd case that the test writers do throw in some other punctuation errors, you should know what to expect. The ACT officially states that it covers, in addition to the punctuation mentioned above, the following punctuation marks:
Parentheses and Dashes
Parentheses usually surround words or phrases that break a sentence’s train of thought but provide explanatory information for it. For example,

Their road trip (which they made in a convertible) lasted three weeks and spanned fourteen states.

Similarly, parenthetical sentences can be inserted between other sentences, adding additional information to them without diverting their flow. For example,

Their road trip lasted three weeks and spanned fourteen states. (The one they took two years ago lasted two weeks and covered ten states.) When they got home, they were exhausted.

In this example, the parenthetical information about the previous road trip is interesting but not completely relevant to the other sentences. Note that when an entire sentence is enclosed within parentheses, the period should be inside them as well.
Dashes function similarly to parentheses. Dashes indicate either an abrupt break in thought or an insertion of additional, explanatory information.

He walked so slowly—with his lame leg he couldn’t go much faster—that even his neighbor’s toddler eventually overtook him.

I don’t have the heart to refuse a friend’s request for help—do you?

Periods, Question Marks, and Exclamation Points
These are the least common forms of punctuation tested by the ACT. The ACT writers probably realized that these sentence enders are easier to grasp than other forms of punctuation because they basically each have only one function:

The sentence ends here.

Does the sentence end here?

Hooray, the sentence ends here!

The period in the first example indicates that the sentence has ended. In the second example, the question mark indicates that a question is being asked. The third example is an exclamatory statement marked by an exclamation point. Exclamation points should be used sparingly to indicate statements made with great emotion (for example, anger, excitement, or agitation).
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