Punctuation means standard marks and signs in writing and printing to separate words into sentences, clauses, and phrases in order to clarify meaning. A properly punctuated sentence will help the reader understand the organization of the writer’s ideas.
The ACT English test includes questions that address both the rules and usage of punctuation. You should be able to identify and correct errors involving the following punctuation marks:
A comma is used to indicate a separation of ideas or elements within a sentence.
1.1 Use a comma with a coordinating conjunction to separate independent clauses within a sentence.
A coordinating conjunction connects words, phrases, or clauses that are of equal importance in the sentence. For example,
1.2 Use a comma to separate elements that introduce and modify a sentence.
1.3 Use commas before and after a parenthetical expression.
A parenthetical expression is a phrase that is inserted into the writer’s train of thought. Parenthetical expressions are most often set off with commas. For example,
1.4 Use commas before and after an appositive.
An appositive is a noun or phrase that renames the noun that precedes it. For example,
1.5 Use a comma to set off an interjection.
1.6 Use commas to separate coordinate adjectives.
If two adjectives modify a noun in the same way, they are called coordinate adjectives. Coordinate adjectives can also be joined with and (without a comma). For example,
1.7 Use commas to set off a nonrestrictive phrase or clause.
A nonrestrictive phrase or clause is one that can be omitted from the sentence without changing the meaning of the sentence. Nonrestrictive clauses are useful because they serve to further describe the nouns that they follow. For example,
1.8 Use a comma to separate items in a list or series.
1.9 Use commas in dates, addresses, place names, numbers, and quotations.
Commas generally separate a quotation from its source. For example,
Do not use a comma:
- to separate a subject from a verb.
The police officer walked down to the corner.
NOT - The police officer, walked down to the corner.
- to separate an adjective from the word it modifies.
The pretty girl sat in front of me on the bus.
NOT - The pretty, girl sat in front of me on the bus.
- before a coordinate conjunction and a phrase (NOT an independent clause with its own subject and a verb).
Jeff likes to relax on his couch and listen to music.
NOT - Jeff likes to relax on his couch, and listen to music.
- to separate two independent clauses; this is known as a comma splice.
I plan to attend a liberal arts college. My parents want me to get a well-rounded education.
NOT - I plan to attend a liberal arts college, my parents want me to get a well-rounded education.
An apostrophe is used to form possessives of nouns, to show the omission of letters in contractions, and to form plurals of letters and numbers with 's'.
2.1 Add an apostrophe and an 's' to form the possessive of singular nouns, plural nouns, or indefinite pronouns that do not end in 's'.
2.2 Add an apostrophe to form the possessive of plural nouns ending in 's'.
2.3 Add an apostrophe to the last noun to indicate joint possession.
2.4 Add an apostrophe to all nouns to indicate individual possession.
2.5 Add an apostrophe to indicate contractions.
2.6 Add an apostrophe to form the plural of letters and numbers.
2.7 Do not use an apostrophe with a possessive pronoun.
The car with the flat tire is ours.
NOT - The car with the flat tire is our’s.
Yours is the dog that barks all night.
NOT - Your’s is the dog that barks all night.
A colon is used before a list or after an independent clause that is followed by information that directly modifies or adds to the clause. An independent clause can stand alone as a complete sentence.
A semicolon is used to join closely related independent clauses when a coordinate conjunction is not used, with conjunctive adverbs to join main clauses, to separate items in a series that contains commas, and to separate coordinate clauses when they are joined by transitional words or phrases.
3.1 Use a colon before a list.
3.2 Use a colon after an independent clause that is followed by information that directly modifies or adds to the clause.
3.3 Colons may also precede direct quotations and should be used in business salutations and titles.
3.4 Use a semicolon to join closely related independent clauses when a coordinate conjunction is not used.
3.5 Use a semicolon with conjunctive adverbs to join independent clauses.
3.6 Use a semicolon to separate items that contain commas and are arranged in series.
3.7 Use a semicolon to separate coordinate clauses when they are joined by transitional words or phrases.
When a sentence contains more than one clause, each of which is considered equally as important as the other, the clauses are called “coordinate clauses.” They are typically joined by a coordinating conjunction, such as and, but, or, so. When a coordinating conjunction is not used, a semicolon should be.
Parentheses are used to enclose supplemental information that is not essential to the meaning of the sentence. Dashes are used to place special emphasis on a certain word or phrase within a sentence.
4.1 Use parentheses to enclose explanatory or secondary supporting details.
4.2 Use dashes in place of parentheses to place special emphasis on certain words or phrases.
Periods, question marks, and exclamation points are considered 'end punctuation' and should be used at the end of a sentence.
5.1 Use a period to end most sentences.
5.2 Use a question mark to end a direct question.
5.3 Use an exclamation point to end an emphatic statement.