Common Grammar Errors

Grammar errors sneak into almost all writing. Some writers like to think they don’t make mistakes — but their editors know better. The following errors are among the most common:

  1. Split infinitives
  2. Adverb usage
  3. Subject-verb agreement
  4. Pronoun agreement
  5. Pronoun case
  6. Apostrophe usage
  7. Dangling modifiers
  8. Double negatives
  9. Sentence structure
  10. Comma and semicolon usage

It should be stated that the label error is subjective at times. English purists might want to freeze elements of the language, but the dynamic nature of English is what makes it an interesting language. What is unacceptable today might be part of U.S. Standard English or International (U.K.) English in a generation. The first rule we explore below illustrates this evolutionary nature of English.

Split Infinitives

In speech, Americans tend to insert adverbs between to and the verb in an infinitive. Because this tendency has existed for a long time, it sounds correct to most people. Writers are guilty of perpetuating this error, especially copywriters working in advertising. Honestly, it does sound awkward when some adverbs are relocated to before or after a verb phrase.

Revising sentences to avoid split infinitives and split verb phrases can result in writing that seems pretentious to readers.

When writing dialogue, a writer must create believable characters. For this reason it is unrealistic to expect the removal of all split infinitives from any work of fiction. Our request is that writers attempt to remove split infinitives from those sections of text that are not dialogue or internal thought. Also, any academic work should adhere to the rule. Mass audience periodicals often accept the split infinitive within narrative, so it seems the rule is fading.

Common split infinitives include:

to quickly go

to angrily say

to impatiently wait

No split is as famous in America as to boldly go — and we cannot imagine Star Trek opening with to go boldly even if that is correct. The adverb in these verb phrases should follow the verb. In some cases it is possible to place the adverb before the infinitive. We suggest reading the sentence alound to determine how natural the revision is. If it sounds better with the split infinitive, then you need to ask yourself about the intended audience.


A tendency toward hyperbole results in the misuse of adverbs in both spoken and written English. Some individuals believe it necessary to modify verbs to convey strong ideas. Accurate and concise descriptions are more effective. See our rather aggressively named Words to Kill for more information.


Adverbs should not be used when precise descriptions are possible. For example, the word very can be replaced or omitted in most sentences. Some adverbs are precise and possess the strength of adjectives. The adverb weekly indicates a precision that often lacks. Always favor adverbs with specific meanings, not loose implications. There are times when adverbs of frequency or degree remain vague necessarily.


Adverbs ending in -ly are often misspelled or left in their truncated adjective forms. Speakers and writers tend to omit the -ly suffix. Commonly truncated adverbs include: differently, quickly, and slowly.

Subject-Verb Agreement

There are singular and plural verbs in addition to singular and plural nouns. A singular verb must be used with a singular subject and a plural verb used with a plural subject. While this seems obvious, the construct escapes some students. Many singular verbs end with the letter s while plural nouns end in s as well.

The cat dreams about chasing mice.

The cats dream about chasing mice.

It is not always easy to match subject and verb quantities. Also, International English and U.S. Standard English disagree on how to treat collective nouns. Though some teachers and editors might dislike this advice, we have found that if a word processor detects a verb error the suggested correction tends to be accurate.

Apostrophe Usage

Apostrophes are misused often, especially when forming possessive forms of nouns. Some people forget to use an apostrophe, while others are so afraid of forgetting they use apostrophes with abandon.


Add an apostrophe and an s to singular nouns to indication possession. According to several current grammar texts, add the apostrophe after the letter s to indicate a plural possessive, unless the dual s sounds are pronounced. It is also standard to use the apostrophe s with Biblical names, probably out of tradition more than for reasons of phonology or grammar.

He located the cats toy under the chair.

The cats toys were tattered after years of play.

The Smiths two cats chased the Wilsons dog.

Plural possessives can be challenging:

The Williamsess dogs chase cats. (Strunk & White style)

The Williamses dogs chase cats. (AP Stylebook and MLA version)

The first version of the last example looks odd to many readers. Strunk and White suggest the apostrophe plus s, AP Style omits the last s. We tend to pronounce the -ez sound instinctively when it helps clarify the quantity of the noun. The last s desired by Strunk and White is seldom vocalized. The second version, without the s, is more common and closer to the spoken version of the sentence.


A verb contraction shortens a verb or verb phrase, matching informal English speech. Contractions join with verbs or pronouns. Avoiding contractions when writing fiction results in stilted dialog, whereas using too many reduces the effectiveness of writing. In academic writing, contractions might be disallowed by tradition, official style, or by an individual instructor. Always verify the preference of an editor or instructor.

Ain’t is never the contraction for am not or is not. While some defend the use of ain't for am not as no more irregular than won’t for will not, no authority seems to accept this argument.

The Big Error: Word Confusion

The most common apostrophe errors are confusing it’s and its or who’s and whose. The possessive forms of these pronouns do not use an apostrophe, while the verb contractions do use apostrophes.

Its hair is long and black. I think it’s a beautiful cat.

Whose car is that? More importantly, who’s the woman driving?

In addition to the four words listed above, you can guess the other problem pairs: they’re/their and you’re/your. Use an apostrophe for the contractions of are.


Because we use pronouns to simplify communication, it is hard to remember how complex the usage rules can be. Beyond ensuring that the relationship between a pronoun and its antecedent is clear, you should verify agreement and pronoun case.


Pronouns should agree with their antecedents. He, she, his, her, and their are confused by many writers. When you see their in a sentence about each or every, it is probably incorrect.

Each student is asked to bring his or her supplies to class.


Each student is asked to bring their supplies to class.


Students should bring supplies to class.

Each is a singular pronoun antecedent, requiring a singular mate. In English, we use his or her to indicate a gender-neutral subject.

Pronoun Case

Pronoun case refers to the pronoun’s status as a subject, indirect object, or direct object. There is a tendency to use the subjective case when the objective is correct. Some writers think it sounds more refined to use I, he, or she in the objective position within some sentences; it is incorrect, not refined.

Subject Object
I me
we us
you you
he him
she her
it it
they them
who whom
thou thee

I wondered what came over me.

He waited an hour for her to arrive, and then she ignored him.

Many of us struggle with who versus whom when writing. The easiest test is if you can substitute him or them in place of whom.

She sent the manuscript to them? = She sent the manuscript to whom?

He is in charge right now? = Who is in charge right now?

Dangling Modifiers

Located at the beginning of clauses, dangling modifiers present a challenge for most writers. When they appear at the beginning of sentences, dangling modifiers are associated with the first noun in the independent clause.

Screaming all the way, the roller coaster thrilled us.

The preceding example implies the roller coaster was screaming, resulting in a thrill for the riders. It should be clear the riders are screaming, not the coaster. Consider:

Screaming all the way, we were thrilled by the roller coaster.

Double Negatives

Although most languages feature double negatives, standard forms of English do not. Unfortunately, double negatives are used in conversation and popular culture, often for emphasis or in sarcasm. The vernacular contraction ain’t often appears in double negatives.

I ain’t no grammar expert.

He don’t know nothing about the robbery.

He doesn’t know nothing about the robbery.

The proper constructions are to either use the negative adverb or a noun of negation.

I am not a grammar expert.

He doesn’t know anything about the robbery.

He knows nothing about the robbery.

Sentence Structure

Sentence structures can confuse even the most experienced writers. With sentences, the adage of knowing the rules before breaking them is valuable advice. It also helps to understand that sentence structures have changed and will continue changing over time. Simply because an early English work includes all manner of sentence structures does not mean a modern writer can ignore today’s standards recklessly.

Run-On Sentences

Run-on sentences feature fused joins, comma splices, or conjunctions linking more than two independent clauses. The run-on is a problem because it presents two or more ideas as a single thought, even if the ideas are only loosely related.

Many basic grammar guides consider the overuse of conjunctions a form of run-on sentence, even when the abuse of conjunctions is other than joining three or more independent clauses. Once a young student learns to use and to combine ideas, the sentences seem to run on for a few years. Many of us continue this habit in our daily speech for the rest of our lives. If you notice a high percentage of commas and conjunctions in your writing, you might have run-on sentences.

Basic Run-On

The basic run-on is an error caused by joining two or more independent clauses with only a coordinating conjunction (and, but, or, nor, for, so, yet). The common fix is to add a comma or semi-colon before the conjunction. An easier fix is to rewrite the sentence as two or more complete sentences.

Fused Sentences

Fused sentences are two independent clauses joined without punctuation or a conjunction. See the discussion of commas and semicolons for a variation on problems with independent clauses. An independent clause is a complete sentence, with both subject and verb. When connecting two independent clauses, some form of punctuation is required.

Lisa walked along the beach she liked the sounds of the ocean.

When the cars raced by we cheered it was an exciting race.

The example sentences can be corrected with either punctuation or the use of a well-placed conjunction. The easiest way to correct fused sentences is to insert periods or semicolons.

Lisa walked along the beach. She liked the sounds of the ocean.

When the cars raced by we cheered; it was an exciting race.

Comma Splices

A comma splice is the joining of two independent clauses (sentences) with a comma. A semicolon can join two related independent clauses when the second clause reinforces the first and need not stand alone. If a semicolon is not appropriate, then create two sentences.

Samantha went to the store. She forgot to buy milk.


Samantha went to the store; she forgot to buy milk.


Samantha went to the store, and she forgot to buy milk.


Samantha went to the store, she forgot to buy milk.

Sentence Fragments

A sentence fragment is a dependent clause or phrase used by a writer as a complete sentence. Fragments pose a unique problem because they are an accepted form in literary works. The best rule for fiction writers is see if the fragment sounds “right” in a given text.

Rachael listened for the sound of footsteps. Nothing. In fact, there were none of the normal sounds of night. Absolute silence.

Commas and Semicolons

Some writers avoid commas altogether. While this is safe if you write simple sentences, more complex constructions will require some brave comma use and the occasional semicolon. The problem for many students is the reckless insertion of commas after they overcome their fear of punctuation marks.


For most lists, use commas. Only use semicolons when commas create confusion. There is some debate as to whether or not a comma is required before the conjunction. We suggest using the comma, but some grammarians insist it is not needed. We think the comma prevents confusion, especially when some items in the list might include conjunctions.

The breakfast menu included ham and eggs, pancakes, omelets, and french toast.


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Writer: C. S. Wyatt
Updated: 08-Mar-2017
Editor: S. D. Schnelbach