Common Grammar Mistakes

Writers are often faced with challenges concerning grammar. The best ways to overcome these challenges are to learn the rules and to practice. When certain grammatical mistakes keep reappearing, they should be addressed specifically. This handout reviews common grammar problems and provides examples to help clarify the rules.

Basic Subject/Verb Agreement

A subject and verb must match in number and person. Singular subjects do not end in -s or -es, but plural subjects do. Verbs follow the opposite pattern: singular verbs end in -s or -es, while plural verbs do not.

Examples:

That student agrees that professors assign too much reading.
College students read all day and half the night.
Buses carry students from home to class and from class to work.
The red double-decker bus carries tourists throughout London.

Additional information and examples can be found in A Writer’s Reference, pp. 353–60.

Wrong or Missing Verb Ending

Verb endings such as -s, -es, -ed, or -d are sometimes forgotten because they are not always pronounced. Writers must add the correct ending to match the tense.

Incorrect → Correct:

Eliot use feline imagery → Eliot uses feline imagery
The professor often discuss imagery → The professor often discusses imagery
Nobody imagine he would win → Nobody imagined he would win
The students ask the college → The students asked the college

See A Writer’s Reference, pp. 363–64.

Sentence Fragment

A sentence fragment usually lacks a subject, a verb, or both, or begins with a subordinating word.

Examples:

Lacks subject: Marie Antoinette spent huge sums of money. Helped bring on the French Revolution.
Lacks complete verb: The old aluminum boat sitting on its trailer.
Subordinating word: We returned to the drugstore. Where we waited.

See A Writer’s Reference, pp. 385–90.

Run-On Sentences

Run-on sentences occur when independent clauses are joined without proper punctuation. They can be fixed by separating the clauses, using a comma with a coordinating conjunction, or using a semicolon.

Examples:

The current was swift; he could not swim to shore.
Klee’s paintings seem simple, but they are sophisticated.
She doubted meditation; nevertheless, she tried it.

See A Writer’s Reference, pp. 390–94.

Missing or Misplaced Possessive Apostrophe

Apostrophes show ownership. Use ’s for singular nouns and plural nouns not ending in -s, and use only an apostrophe for plural nouns ending in -s.

Incorrect → Correct:

a childs well-being → a child’s well-being
anybodies’ guess → anybody’s guess
Childrens costumes → Children’s costumes
Yankee’s pitcher → Yankees’ pitcher
the Stearns’ home → the Stearnses’ home

See A Writer’s Reference, pp. 451–54.

Its / It’s Confusion

Its is possessive. It’s is a contraction meaning it is or it has. Possessive pronouns do not use apostrophes.

The car lay on its side.
It’s a white Buick.
It’s been there for two days.

See A Writer’s Reference, pp. 454–65.

Incorrect or Missing Preposition

Prepositions convey specific meanings. Using the wrong one—or omitting one—can change meaning.

compared with a helpless giant
refused to comply with regulations
curiosity about how things work

See A Writer’s Reference, pp. 425–28.

Unnecessary Shifts in Verb Tense

Avoid shifting between time periods without reason.

Lucy was watching the bird when she slipped and fell.
Each team is assigned cases and investigates them.

See A Writer’s Reference, pp. 316–17.

Unnecessary Shifts in Pronoun

Pronouns should not shift without reason, especially from one to you or I.

When one sees a painting, one is impressed.
If we had known, we would have acted.

Vague Pronoun Reference

Pronouns must clearly refer to a specific word. Ambiguous references confuse readers.

Clarify which person she refers to.
Specify what this refers to.

Lack of Agreement Between Pronoun and Antecedent

Pronouns must agree in number and gender with their antecedents.

Every student must bring his or her book.
The team changed its strategy.

Comma Errors

Missing Comma in a Series

Use commas between three or more parallel items.

Missing Comma After an Introductory Element

Use a comma after introductory words, phrases, or clauses.

Comma Splices

Do not join independent clauses with a comma alone.

Restrictive vs. Nonrestrictive Elements

Use commas around nonessential information; do not use commas with essential information.

Principal Misuses of Commas

Do not separate subjects from verbs.
Do not place commas after conjunctions.
Do not interrupt indirect quotations.

See A Writer’s Reference, pp. 435–47, and The Little, Brown Handbook.