Skip to Main Content

Citation Help

Learn to cite your sources correctly.

Grammar Refresher

Learn to Write

This page covers common mistakes in English prose. For more extensive help with writing and grammar, contact the Academic Success Center.

For style-specific rules, see this guide’s subsequent pages.

Sentence Structure

Subject + Verb

With exceedingly rare exceptions, every sentence requires a subject and a verb. A subject is a noun, pronoun, or determiner that performs the action of the verb.

He runs.

The defense rests.

Subject + Verb + Object

Direct Objects

A direct object is a noun, pronoun, or determiner that the verb modifies.

Steve drove the car.

Some verbs, called transitive verbs, require objects. The oft-confused verbs lie and lay are good examples of the difference between transitive and instransitive verbs:

I will lie on the sofa.

I lay on the sofa.


I will lay this on the floor.

I laid the dishes on the table.

Indirect Objects

An indirect object is an object the verb indirectly modifies. In this sentence, me is an example:

Sally gave me the ball.

Passive Voice

Passive voice happens when you treat an object as if it is a subject.

The meeting will be held at seven o’clock.

In this example, the subject of the verb phrase will be held is the meeting, which is the object of the action (holding).

We could rewrite this example as:

We will hold the meeting at seven.


The meeting is at seven.

These examples are in active voice because the subject (We or the meeting) clearly takes the verb. Active sentences sound more assertive than passive ones.

Passive voice is not incorrect. However, if you overuse it, your writing will sound wordy and weak. As you edit, rephrase passive sentences as active ones when possible.

In Academic Prose

Previously, passive voice was common in academic literature, especially in the hard sciences, because the performer of the verb (that is, the scientist) is unimportant to an experiment:

In the next step, 10 ml of hydrochloric acid were added to the solution.

This is still widely accepted. However, it is good practice even in academic writing to avoid passive voice when it is reasonable to do so.

Comma Rules

The comma is the most versatile—and misused—punctuation mark.

Independent Clauses

An independent clause is a clause that could form a complete sentence on its own. You can link it to another independent clause with a comma and a coordinating conjunction. This is called a compound sentence.

He ran a marathon, and she lifted weights.

I used commas correctly in only three sentences, but that’s the best I could do.

There are seven coordinating conjunctions, which you can remember with the mnemonic FANBOYS:

  • For
  • And
  • Nor
  • But
  • Or
  • Yet
  • So

However, you should avoid placing a comma between a subject and its verb:

He tried to scramble out of the pit but quickly fell back down.

In this example, quickly fell back down is not an independent clause because it contains no subject, so a comma is unnecessary.

Dependent Clauses

A dependent clause cannot stand on its own as a sentence but is connected to an independent clause with a subordinating conjunction. This forms a complex sentence.

The dependent clause can either precede or follow the independent clause. When it follows, it does not require a comma:

I walked to the coffee shop because I was hungry.

If the dependent clause precedes the dependent clause, the comma is necessary:

Because I was hungry, I walked to the coffee shop.

Writers sometimes use a comma to separate a dependent clause in cases of extreme contrast. This is an optional stylistic choice supported by most grammarians.

I finally got in the car, though I hated having to go.


Use commas to separate items in a list:

We bought magoes, strawberries, grapefruits, and potato chips.

The Oxford Comma

The word and or or precedes the final item in a list. Whether a comma belongs before this conjunction is the subject of vigorous debate. Some consider this so-called “Oxford comma” unnecessary, but others insist it aids clarity.

Your style guide may dictate Oxford comma use: Chicago, MLA, and APA styles all recommend it, but AP style recommends against it.

Coordinate Adjectives

When two or more adjectives describe a noun equally and in the same way, separate the adjectives with commas.

The aging, decrepit house looked ominous.

To determine whether adjectives are coordinate, try changing the order.

He drove a used sports car.

In this example, the adjective sports is a qualifier to the noun car, so the two act as a single unit. If the order of adjectives is changed, the sentence becomes unintelligible:

He drove a sports used car.

This indicates that a comma does not belong between the adjectives.

Adjective Order

Stylistically, English requires a specific order to adjectives. Most native English speakers use this order habitually, but those who learn English as a second language often struggle with it.

I played with the red big ball.

This sentence is not technically incorrect, but it sounds wrong to a native speaker.

The correct order is:

  1. quantity

  2. opinion

  3. size

  4. age

  5. shape

  6. color

  7. origin or material

  8. qualifier

I have one lovely large old rotund brown Australian blood hound.

Because each of these adjectives falls into a different category, they do not require commas, though commas could be added for clarity.


Separate quoted dialogue from its attribution using a comma, never a period. Note that the comma goes inside the quotation mark:

“I don’t like Brussels sprouts,” she said.


“I don’t like Brussels sprouts!” she cried.

“Why don’t I like Brussels sprouts?” she asked.

Question marks and exclamation points are appropriate between dialogue and attribution. However, you should generally avoid exclamation points in formal writing.

Parenthetical Citations

In parenthetical citations, which are used in APA and MLA academic styles, both the citation and the final punctuation go outside the quotation mark. This is because the citation is part of the sentence but not part of the quote.

Quantum physics has some amazing implications, but it is very much grounded in the physical and the possible, describing processes that are going on in atoms, in computer chips, in lasers, and in nuclear bombs (Schaffer and Lemos 9).

Parenthetical Elements

Use commas to set off statements or interjections that are unnecessary to the meaning of the sentence:

The lecture, which went on for hours, was tedious.

Introductory Addresses and Expressions

Joe, take this to my office.

Oh, to be in Rome!

Locations & Dates

This rule applies to city and state as well as some date formatting:

While standing on a corner in Winslow, Arizona, I saw a fine sight.

On , we traveled from one end of the country to the other.


The incident occurred on .