The twenty most common errors in college writing were identified by Andrea Lunsford and Robert Connors in research examining thousands of student essays in the late 1980s. Explanations of the errors have been adapted from The Everyday Writer by Lunsford and Connors (New York: St. Martin’s Press, 1997, pp. 11–14).

1. 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: In addition to other dissimilarities between the two playwrights' styles Terence and Plautus put their prologues to strikingly different uses.

Correct:   In addition to other dissimilarities between the two playwrights' styles, Terence and Plautus put their prologues to strikingly different uses.

2. Vague pronoun reference
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.

3. Missing comma in a compound sentence
When two independent clauses (clauses that can stand alone as separate sentences) are joined by a coordinating conjunction such as 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: In theatre, pace refers both to tempo and acting intensity and as such the director cannot set the pace of a performance simply by calling for the actors to "pick it up" or "slow it down." Rather, a performance's pace emerges organically out of the actors' understandings and interpretations of their roles.

Correct:   In theatre, pace refers both to tempo and acting intensity, and as such a director cannot set the pace of a performance simply by calling for the actors to "pick it up" or "slow it down." Rather, a performance's pace emerges organically out of the actors' understandings and interpretations of their roles.

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 theatre, pace refers both to tempo and acting intensity, and so cannot be imposed onto a performance.

Correct:   In theatre, pace refers both to tempo and acting intensity and so cannot be imposed onto a performance.

4. 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: Both Plautus and Terence drew heavily from Greek "New Comedy" for there materials and stories, neither used a chorus, and both incorporated multiple leading rolls.

Correct:   Both Plautus and Terence drew heavily from Greek "New Comedy" for their materials and stories, neither used a chorus, and both incorporated multiple leading roles.

5. 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 is underlined. The intended message of this sentence is that none of the audience members had experienced this type of production and so all were transfixed. Without the restricting commas, the sentence would read as though only a subset of the theatre goers seemed transfixed.

Incorrect: The audience members who had never seen a production of this type were transfixed by the performance.

Correct:   The audience members, who had never seen a production of this type, were transfixed by the performance.

6. Wrong or missing verb ending (-s or -es, -d or -ed)
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. (See also #10.)

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.

7. 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: The two actors first met 20 years ago while walking in Main Street at Ashland, Oregon.

Correct:   The two actors first met 20 years ago while walking along Main Street in Ashland, Oregon.

8. 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; or (4) by rewriting the sentence to subordinate or eliminate one of the independent clauses.

Incorrect: The splendid Stuart masques were staggeringly expensive, one such production cost 21,000 pounds at a time when a skilled worker's annual earnings were about 25 pounds.

Correct:   The splendid Stuart masques were staggeringly expensive. One such production cost 21,000 pounds at a time when a skilled worker's annual earnings were about 25 pounds.
or
The splendid Stuart masques were staggeringly expensive; one such production cost 21,000 pounds at a time when a skilled worker's annual earnings were about 25 pounds.
or
The splendid Stuart masques were staggeringly expensive, and in fact, one such production cost 21,000 pounds at a time when a skilled worker's annual earnings were about 25 pounds.
or
The splendid Stuart masques were staggeringly expensive, one such production costing 21,000 pounds at a time when a skilled worker's annual earnings were about 25 pounds.

9. Missing or misplaced possessive apostrophe
Possessive nouns (nouns that indicate possession of something else) generally have an apostrophe-s ending if singular (e.g. playwright's or actress's) or just an apostrophe if plural (e.g. playwrights' or actresses'). Possessive personal pronouns (e.g. hers, his, ours, theirs, yours, and its), however, do not take apostrophes.

Incorrect: Mime was both Romes most popular and it's most notorious theatrical entertainment during the Empire.

Correct:   Mime was both Rome's most popular and its most notorious theatrical entertainment during the Empire.

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

Incorrect: While the impressionist playwrights of the 1890s sought to create a pleasantly dreamlike stage world, the surreal expressionist theatre productions of the early 1900s can more aptly be described as nightmarish.

Correct:   While the impressionist playwrights of the 1890s sought to create a pleasantly dreamlike stage world, the surreal expressionist theatre productions of the early 1900s could more aptly be described as nightmarish.

11. Unnecessary shift in pronoun
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: When you have completed this chapter, one should be able to define Romanticism.

Correct:   When you have completed this chapter, you should be able to define Romanticism.

12. Sentence fragment
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: One characteristic of the feminist theatre movement of the 1970s was its preference for a leaderless, communal style of organization. The reason being that the traditionally hierarchical organization of the theatre valorizes and promotes the masculine-associated trait of competitiveness, whereas collectivity involves and evokes cooperation, a quality associated with the feminine.

Correct:   One characteristic of the feminist theatre movement of the 1970s was its preference for a leaderless, communal style of organization, the reason being that the traditionally hierarchical organization of the theatre valorizes and promotes the masculine-associated trait of competitiveness, whereas collectivity involves and evokes cooperation, a quality associated with the feminine.
or
One characteristic of the feminist theatre movement of the 1970s was its preference for a leaderless, communal style of organization. The reason for this preference was that the traditionally hierarchical organization of theatre valorizes and promotes the masculine-associated trait of competitiveness, whereas collectivity involves and evokes cooperation, a quality associated with the feminine.

13. Wrong tense or verb form
The verbs in a sentence must clearly communicate whether the condition or action being reported in the sentence is happening in the past, present, or future, whether the action is definite or conditional, and so on. Be on the alert for irregular verbs (verbs that don't follow the standard pattern for indicating tense) that have been treated as regular verbs.

Incorrect: Plays are fascinating expressions of creativity; they were both made and wrote.

Correct:   Plays are fascinating expressions of creativity; they are both made and written.

14. 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: Courses in playwriting help acquaint theatre students with the challenges faced by playwrights and provides insights on other elements of theatre such as acting, stage direction, and design.

Correct:   Courses in playwriting help acquaint theatre students with the challenges faced by playwrights and provide insights on other elements of theatre such as acting, stage direction, and design.

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:   Both the producer and the director have already met with the cast to discuss the unexpected change in venue.

Correct:   The play's producer and director has already met with the cast to discuss the unexpected change in venue.

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

Correct:   Neither the director nor the actors were prepared for the difficulties of accommodating the unexpected change in venue.

15. 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: African playwrights have written plays in tribal, national and international (colonial) languages.

Correct:   African playwrights have written plays in tribal, national, and international (colonial) languages.

16. Lack of agreement between pronoun and antecedent
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: In Long Day's Journey, James Tyrone and his first-born son constantly project his own fears onto one another.

Correct:   In Long Day's Journey, James Tyrone and his first-born son constantly project their own fears onto one another.

Note also that the words each, every, one, none, 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: As well as denying Mary's drug addiction, each of the three men in the Tyrone family also have a severe problem with alcohol abuse that they refuse to acknowledge.

Correct:   As well as denying Mary's drug addiction, each of the three men in the Tyrone family also has a severe problem with alcohol abuse that he refuses to acknowledge.

Incorrect: Neither James Jr. nor Edmund Tyrone entirely respect their father or—even more significantly—themselves.

Correct:   Neither James Jr. nor Edmund Tyrone entirely respects his father or—even more significantly—himself.

In the case of subject parts joined by or or nor, agreement should be with the part closest to the verb.

Correct:   Neither Mary Tyrone's husband nor her sons are willing to acknowledge the ways in which all three men are implicated in Mary's retreat into drug addiction.

Some noun antecedents (for example, "director" or "playwright") are non-gender-specific; that is, these words refer to both males and females. When you use this type of antecedent in its singular form, your 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: In this production of Long Day's Journey, each actor performs his part brilliantly.

Correct:   In this production of Long Day's Journey, each actor performs his or her part brilliantly.
or
In this production of Long Day's Journey, all of the actors perform their parts brilliantly.
or
In this production of Long Day's Journey, every actor delivers a brilliant performance.

17. Unnecessary comma(s) with a restrictive element
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 Moliere wrote only one comedy but that this specific comedy depicts a particular type of ludicrous human being.

Incorrect: Moliere's comedy, Tartuffe, depicts characters made ludicrous by their deviations from decorum.

Correct:   Moliere's comedy Tartuffe depicts characters made ludicrous by their deviations from decorum.

18. Fused sentence
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; or (4) rewrite the sentence to subordinate or eliminate one of the independent clauses.

Incorrect: Wagner disagreed with the idea that theatre should faithfully reproduce everyday life rather, he argued, drama should depict an ideal world based on the culture's history and myths.

Correct:   Wagner disagreed with the idea that theatre should faithfully reproduce everyday life. Rather, he argued, drama should depict an ideal world based on the culture's history and myths.
or
Wagner disagreed with the idea that theatre should faithfully reproduce everyday life; rather, he argued, drama should depict an ideal world based on the culture's history and myths.
or
Wagner disagreed with the idea that theatre should faithfully reproduce everyday life, and he argued instead that drama should depict an ideal world based on the culture's history and myths.
or
Disagreeing with the idea that theatre should faithfully reproduce everyday life, Wagner argued instead that drama should depict an ideal world based on the culture's history and myths.

19. 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: The playgoers watched as the actress sauntered across the stage, fanning their programs.

Correct:   Fanning their programs, the playgoers watched as the actress sauntered across the stage.

20. Its/It's confusion
Its indicates possession; it's is a contracted form of it is or it has.

Incorrect: A melodrama always aligns it's characters according to morality.

Correct:   A melodrama always aligns its characters according to morality.

A number of these sample sentences were adapted from The Enjoyment of Theatre by Kenneth M. Cameron and Patti P. Gillespie (4th ed., Needham Heights, MA: Allyn & Bacon, 1996). Handout prepared by Jocelyn Henderson, Oregon State University, 1998; revised and edited by Tracy Ann Robinson. With thanks to Dr. Charlotte Headrick, OSU Department of Speech Communication, for her content review.