Errors in grammar and usage detract from your writing and may cause the reader to question your authority as a writer. Use these proofreading tips and edit for the twenty most common errors identified in a study by Lunsford and Connors.

Proofreading Tips

Read your paper aloud; it’s easier to “hear” the mistakes than to see them. Or, try reading your paper backwards, sentence by sentence. That way your mind will focus on the proofreading rather than the content.

Keep a log of the errors you make frequently and spend some time with a handbook or in the Writing Center in order to understand your frequent errors and correct them in your writing.

Check for Common Errors

The following is a list of common grammar errors. Examples that are specific to certain disciplines can be found here.

Comma Problems

Missing comma after an introductory element

Many sentences begin with one or more introductory elements—clauses, phrases, or single words that lead into the main body of the sentence. To show where an introductory element ends and the main part of the sentence begins (thus helping your readers move more easily through the sentence), insert a comma after the introductory element. If the sentence includes multiple introductory elements, use a comma after each one.

Incorrect Collectively the cashew usually ranks as the third or fourth greatest nut of commerce (by mass) worldwide.
Correct Collectively, the cashew usually ranks as the third or fourth greatest nut of commerce (by mass) worldwide.

 

Incorrect If Shelly writes her report on Middlemarch, I will want to read it myself.
Correct If Shelly writes her report on Middlemarch, I will want to read the novel myself.

Missing comma in a compound sentence

When two independent clauses (clauses that can stand alone as separate sentences) are joined by a coordinating conjunction (and, but, so, yet, nor, or for) precede the conjunction with a comma to signal a pause between the two parts of the sentence. The pause gives pace to the sentence and helps prevent sentence misreadings.

Incorrect Dividends were paid in 2001 but the company reported a net loss in income.
Correct Dividends were paid in 2001, but the company reported a net loss in income.

Note: Be sure to distinguish between compound sentences, as defined above, and sentences that have two or more predicate phrases but only one subject. Sentences with a compound predicate do not take a comma between the two parts of the predicate. For example:

Incorrect In 2001, the company both paid dividends, and reported a net loss in income.
Correct In 2001, the company both paid dividends and reported a net loss in income.

Missing comma(s) with a non-restrictive element

Non-restrictive elements are words, phrases, and clauses that provide relevant information in a sentence but are not essential to the sentence’s basic meaning. Non-restrictive elements in a sentence should be set off (on both sides) with commas. In the following example, the non-restrictive element (a phrase modifying heterosis) is underlined.

Incorrect The opposite of heterosis or outbreeding is inbreeding.
Correct The opposite of heterosis, or outbreeding, is inbreeding.

Missing comma in a series

To avoid potential sentence misreadings, always insert a comma between the last two items in a three-or-more-item list.

Incorrect Gram, acid-fast and endospore staining are differential staining procedures.
Correct Gram, acid-fast, and endospore staining are differential staining procedures.

Comma Splice

Inexperienced writers sometimes combine two or more independent clauses (clauses that are capable of standing independently as separate sentences) into a single sentence by inserting a comma between the clauses. This error can be corrected in several ways:

  1. by separating the clauses into stand-alone sentences.
  2. by replacing the comma with a semicolon.
  3. by following the comma with a coordinating conjunction such as and, but, so, yet, nor, or for.
  4. by rewriting the sentence to subordinate or eliminate one of the independent clauses.
Incorrect To believe that freedom of expression is universally available is naïve and unrealistic as the old saw goes, "The right to a free press belongs to those who own the press."
Correct

To believe that freedom of expression is universally available is naïve and unrealistic. As the old saw goes, "The right to a free press belongs to those who own the press."

or

To believe that freedom of expression is universally available is naïve and unrealistic; as the old saw goes, "The right to a free press belongs to those who own the press."

or

To believe that freedom of expression is universally available is naïve and unrealistic, for as the old saw goes, "The right to a free press belongs to those who own the press."

or

To believe that freedom of expression is universally available is naïve and unrealistic, as acknowledged in the old saw that "The right to a free press belongs to those who own the press."

Extra Commas

Restrictive elements are words, phrases, and clauses that are essential to the basic meaning of the sentence. Do not set restrictive elements apart from the rest of the sentence with commas. In the following example, the intended message is not that all sociologists focus on urban social phenomena, but rather that those who do should read Simmel’s essay.

Incorrect Sociologists, who focus on urban social phenomena, should read George Simmel’s essay on “Metropolis and Mental Life” (1902-1903).
Correct Sociologists who focus on urban social phenomena should read George Simmel’s essay on “Metropolis and Mental Life” (1902-1903).

Sentence Problems

Fragments

A sentence fragment is an incomplete portion of a sentence that is punctuated as a full sentence. To correct this error, incorporate the fragment into the preceding or subsequent sentence, or rewrite the fragment as an independent clause. In some types of writing (for example, in fiction and journalistic writing), authors may incorporate fragments as a stylistic choice. In academic writing, however, the use of fragments is far less common.

Incorrect That brief but eye-opening visit to the research laboratory was a turning point in my career. Leading to my decision to pursue virus research.
Correct

That brief but eye-opening visit to the research laboratory was a turning point in my career, for it led to my decision to pursue virus research.

or

That brief but eye-opening visit to the research laboratory was a turning point in my life. The experience led to my decision to pursue virus research.

Lack of Subject-Verb Agreement

The verb form used in a sentence may vary depending on whether the subject is singular or plural and whether the sentence is written in first-, second-, or third person. When you are looking for subject-verb agreement errors, be mindful that the noun closest to the verb may not be the subject.

Incorrect That set of beliefs fly in the face of reason.
Correct That set of beliefs flies in the face of reason.

When the subject consists of two or more nouns connected by and, the subject is generally plural. However, when all parts of the subject refer to the same thing or person, the subject is considered singular (see the second example following).

Correct The men and women who belong to that sect still practice traditions that many of us today consider sexist and discriminatory.
Correct The sect's founder and leader promotes traditions that many of us today consider sexist and discriminatory.

When the subject consists of two or more nouns connected by or or nor, verb agreement should be with the subject noun that is closest to the verb.

Correct Neither the leader nor his followers adhere to the principal of free speech.

Run-ons: Fused, or run-on, sentences occur when clauses that could stand alone are joined with no linking words or punctuation. Correct this error in one of four ways:

  1. Separate the clauses into two (or more) sentences.
  2. Insert a semicolon between the clauses.
  3. Insert a comma followed by a coordinating conjunction (e.g. and, but, so, yet, nor, for) between the clauses.
  4. Rewrite the sentence to subordinate or eliminate one of the independent clauses.
Incorrect We learn about life through our surrounding environment these learned lessons are only part of what shapes our future however.
Correct

We learn about life through our surrounding environment. These learned lessons, however, are only part of what shapes our future.

or

We learn about life through our surrounding environment; these learned lessons are only part of what shapes our future, however.

or

We learn about life through our surrounding environment, but these learned lessons are only part of what shapes our future.

or

Although we learn about life through our surrounding environment, these learned lessons are only part of what shapes our future.

Misplaced or Dangling Modifier

To prevent sentence misreadings, place modifying words and phrases as close as possible to the word or words they modify.

Incorrect She understood better than ever that people are social creatures after reading the textbook.
Correct After reading the textbook, she understood better than ever that people are social creatures.

Verb Problems

Wrong or Missing Verb Ending

In spoken English, we sometimes either omit verb endings altogether or pronounce them inaudibly, but standard written English requires their use even when other information in the sentence implies these endings. Make sure that subject and verb agree (plural or singular) and that you are using the correct verb tense.

Incorrect By "instrument," the actor mean her entire physical self--body and voice--that she use in performance.
Correct By "instrument," the actor means her entire physical self--body and voice--that she uses in performance.

Unnecessary Shift in Verb Tense

Unless you have a clear reason for doing otherwise, use the same tense for all verbs both within and across sentences.

Incorrect Having studied the results, the sociologists report what they found.
Correct Having studied the results, the sociologists reported what they found.

Wrong Verb Tense

A verb must clearly show when a condition or action is, was, or will be completed.

Incorrect The stages of fruit development have included one in which ants were attracted to a specific region of the developing nut.
Correct The stages of fruit development include one in which ants are attracted to a specific region of the developing nut.

Word Choice

Using a Wrong Word

Most instances of this error arise from confusion or carelessness regarding homonyms or other words that either sound similar or have similar meanings. Wrong-word errors may also result from overly casual use of a thesaurus. (Be sure to consult a dictionary if you’re not sure of the exact meaning of a word you find in a thesaurus.)

Incorrect Are interest in cashew began in 1985 with the observation that both single and small groups of cashew trees nationalized around the Calicut district of Kerala, India, were visited by forging ants, spiders, and wasps.
Correct Our interest in cashew began in 1985 with the observation that both single and small groups of cashew trees naturalized around the Calicut district of Kerala, India, were visited by foraging ants, spiders, and wasps.

Wrong or Missing Prepositions

A sentence’s meaning may change depending on the preposition you use in conjunction with a verb or as part of a prepositional phrase. For example, the act of comparing something to something else involves looking for similarities among the two items; the act of comparing something with something else means registering both similarities and differences between the items. The acts of meeting at or in an intersection have different implications, as do the acts of talking around, about, or through an issue.

Incorrect We compared the communities within the biome with one another to identify their common traits.
Correct We compared the communities within the biome to one another to identify their common traits.

Vague Pronouns

Readers should be able to easily identify a pronoun's antecedent (that is, the specific word or phrase to which the pronoun refers). If the antecedent is unclear (either because there is more than one possible pronoun reference or because the word to which the pronoun refers is implied but not actually stated in the text), you need to make the reference more explicit.

Incorrect Although what draws people to theatre and playwriting ultimately remains a mystery, several conditions seem to encourage it.
Correct Although what draws people to theatre and playwriting ultimately remains a mystery, several conditions seem to encourage this attraction.

Incorrect Pronoun Choice

When you use a pronoun reference in a sentence, make sure that you use the same pronoun for all subsequent references in the sentence. The most common example of pronoun shifting is the shift between one and I, you, or we.

Incorrect You can use return-on-assets to measure profitability, but one must consider other ratios as well.
Correct You can use return-on-assets to measure profitability, but you must consider other ratios as well.

Pronoun / Antecedent Agreement

When you use a pronoun (such as you, him, she, their, it) in place of the noun to which it refers (called the pronoun’s antecedent), make sure the pronoun agrees with its antecedent in both gender and number.

Incorrect All species within a given ecological community has its own niche.
Correct All species within a given ecological community have their own niche.

Note that the words each, every, one (and often either and neither) are singular and therefore require singular pronoun references. Also, singular noun antecedents joined by or or nor require a singular pronoun.

Incorrect Within a given ecological community, each species has their own niche.
Correct Within a given ecological community, each species has its own niche.

Some noun antecedents (for example, “ecologist” or “researcher”) are non-gender-specific; that is, they may refer to both males and females. When you use this type of antecedent in its singular form, pronoun references to the antecedent must acknowledge both genders. You have several options for establishing pronoun agreement with non-gender-specific nouns:

  1. For every pronoun reference, use “him and her," “she and he,” etc. Some writers find this awkward and choose instead to alternate between male and female pronoun references either paragraph by paragraph or section by section.
  2. You can change the sentence wording to make the antecedent (and therefore the pronoun) plural.
  3. You can simply get rid of the pronoun. All three solutions are illustrated here.
Incorrect An ecologist generally spends a portion of his work week in the field.
Correct

An ecologist generally spends a portion of his or her work week in the field.

or

Ecologists generally spend a portion of their work week in the field.

or

An ecologist generally spends a portion of the work week in the field.

Apostrophe Problems

Missing or misplaced possessive apostrophe

Possessive nouns (nouns that indicate possession of something else) generally have an apostrophe-s ending if singular (e.g. sociologist's or Davis's) or just an apostrophe if plural (e.g. sociologists' or Davises'). Possessive personal pronouns (hers, his, ours, theirs, yours, its), however, do not take apostrophes.

Incorrect 2 Live Crews artistic world view must be criticized on the basis of a civilly responsible resistance to the bands' rap narrative.
Correct 2 Live Crew's artistic world view must be criticized on the basis of a civilly responsible resistance to the band's rap narrative.

Its / It’s Confusion

Its indicates possession; it’s is a contracted form of it is or it has.

Incorrect Its an interesting study, but the researchers’ methodology definitely has it’s flaws.
Correct It’s an interesting study, but the researchers’ methodology definitely has its flaws.