Eight common grammar errors

There are many grammatical issues to consider when revising your own writing, but this handout focuses on eight of the most common errors that show up in student writing at the university level.

Before we get started, it’s helpful to distinguish between a clause and a phrase. The two terms, which help us name different components of a sentence, come up in our discussions below, so it’s useful to have some working definitions in place.

A clause is a group of words that contains a subject (a noun or pronoun) and a predicate, a term that refers to the verb the subject is performing. You can think of this equation: clause = noun or pronoun + verb.

Clauses can be independent or dependent.

An independent clause is identical to a sentence and makes sense on its own: Maria chased her cat. A dependent (or subordinate) clause contains a subject and a predicate, but it needs to be connected to an independent clause using a subordinating conjunction to make sense: because it got away. Notice that the statement “because it got away” doesn’t make sense on its own: the reader asks, “What got away?” and “What is the ‘because’ explaining?” The dependent clause therefore needs an independent one for the sentence to make sense: Maria chased her cat because it got away.

While a clause contains a subject and a predicate, a phrase does not. The words in a phrase are related, but the phrase is missing a subject-verb combination. For example: After the meeting. Notice how the phrase After the meeting is missing a subject (a noun or pronoun) and a predicate (the verb that noun or pronoun is doing).

The Sentence Fragment

A sentence fragment occurs when 1) a phrase or 2) a dependent clause are used incorrectly to serve as a sentence.

Phrase

I will take you to lunch to discuss further. After the meeting. The second “sentence” in this example is a phrase; it doesn’t contain a subject-verb combination and cannot stand on its own as a grammatical unit. After the meeting is a fragment that needs to be connected to an independent clause to make sense.

To fix this error, we can connect the fragment (the phrase) to a complete sentence (the independent clause) using a comma: After the meeting, I will take you to lunch to discuss further.

Dependent Clause

I have received your printing request. Which our office will complete by Tuesday 4pm. The second “sentence” in this example is a fragment; it’s a dependent clause (signalled by the word “which”) and, as in our first example, needs to be connected to an independent clause to make sense.

To fix this error, we can connect the fragment (the dependent clause) to a complete sentence (the independent clause) using a comma: I have received your printing request, which our office will complete by Tuesday 4pm.

Ask yourself: Does your sentence contain a subject-verb combination? If not, you’ve got a fragment to fix.   

The Comma Splice

A comma splice is an error that occurs when two independent clauses are joined by a comma.

For example: She was late, she called home. This is an error because two grammatically independent ideas (She was late + she called home) have been combined with a comma, when in fact the two independent clauses need to be distinguished from each other.

To fix a comma splice and distinguish between these two ideas, we can add:

• A semicolon
• A period or
• A conjunction 

Corrected, our example would look like this:

• She was late; she called home.
• She was late. She called home.
• She was late, so she called home.

Ask yourself: Are you using a comma to join independent clauses? If so, you’ve got a comma splice to fix.

Run-On Sentence

A run-on sentence occurs when one independent clause follows another without any internal punctuation. For example: He raised his glass he proposed a toast.

To correct a run-on sentence, we need to separate the independent clauses by adding:

• A semicolon
• A period or
• A conjunction 

Corrected, our example would look like this:

• He raised his glass; he proposed a toast.
• He raised his glass. He proposed a toast.
• He raised his glass and proposed a toast.

Ask yourself: How many independent clauses are in each sentence? Are independent clauses properly distinguished from each other?

Its vs. It’s

Its is a personal pronoun that means “belonging to.” For example: The dog eats its bone.

It’s is a contraction of the words “it is.” For example: The pizza is great! It’s delicious. 

Ask yourself: If you replace its/it’s with “it is” does the sentence still make sense? If it makes sense, you need the contraction it’s.

Affect vs. Effect

Most often, affect is used as a verb to mean “have an effect on.” For example: The pandemic and the related pivot to remote learning affected how students learn at university.

When used as a noun, affect means “feeling” or “emotion.” For example: The Shakespearean tragedy elicited strong affect in the audience.

Effect is most often used as a noun to mean “result or consequence.” For example: The effects of climate change are being seen in extreme weather events.

As a verb, effect means “to bring about.” For example: The protesters aim to effect change in the realm of environmental policy.

RAVEN can be used as a mnemonic: Remember Affect Verb Effect Noun

Plurals and Possessives

Plural means more than one; possessive means to belong to. Because both plural nouns and possessive nouns take the letter “s,” confusion sometimes happens about when to add an apostrophe to the “s.” Moreover, some plural nouns can be possessive, which can add to the confusion.

Let’s look at some examples:

The professor marked the student’s paper.

• The apostrophe before the “s” lets us know that it’s one student. Since “paper” is singular, the sentence refers to one student’s single paper.

The professor marked the student’s papers.

• The apostrophe before the “s” lets us know that it’s one student. Since “papers” is plural, the sentence refers to one student’s multiple papers.

The professor marked the students’ paper.

• The apostrophe after the “s” lets us know that it’s more than one student. Since “paper” is singular, the sentence refers to a single paper belonging to multiple students.

The professor marked the students’ papers.

• The apostrophe after the “s” lets us know that it’s more than one student. Since “papers” is plural, the sentence refers to multiple papers belonging to multiple students.

Ask yourself: Is the noun possessive? If so, is the noun singular or plural? 

Parallelism

Parallelism, also known as parallel construction, is a way of creating coherence and style in your writing by grouping like or equal things together: words and words, phrases and phrases, and clauses and clauses.

Notice the difference between these two examples:

Unparallel: Veronica wrote the report quickly, efficiently, and with great accuracy. Parallel: Veronica wrote the report quickly, efficiently, and accurately.

In the unparallel example, of the three things listed, we have two adverbs (quickly, efficiently) and a phrase (with great accuracy). Only two of the three items in this list are similar (the two adverbs); the third item, the phrase, is the odd one out.

Notice that in the parallel example, the list groups together three adverbs to describe how Veronica wrote the report.

In the unparallel sentence, the odd item in the list interrupts the reader, who anticipates a series of like things; but in the parallel example, the reader can more easily follow the text because the like elements (the three adverbs) have been grouped together.

Ask yourself: In lists and around the conjunctions “and” and “or,” have like things been grouped together? Do you hear sounds (like “-ing”) repeated in a list? If not, what item is the odd one out and needs to be revised?

Subject-verb agreement

A verb – an action word – must agree with its subject (the noun or pronoun doing the verb) in both person (I [first person), you [second person], or he, she, it, they etc. [third person]) and number (singular or plural). I like spaghetti and The students play piano are both examples of correct agreement between subject (I, The students) and their verbs (like, play). 

Errors in subject-verb agreement often occur when 1) the sentence order is reversed (that is, the subject comes before the verb) or 2) words come between the subject and the verb.

For example, let’s contrast two examples where the sentence order is reversed:

• Error in subject-verb agreement: Where is Charlotte and her friends on holiday?
• Corrected: Where are Charlotte and her friends on holiday?

Notice in the error the singular verb is used to describe what the plural subject Charlotte and her friends did on holiday. To correct the error, we need to use a plural verb to agree with the plural subject.

Now let’s look at what can happen when words come between the subject and the verb:

• Error in subject-verb agreement: She, along with my other group members, are speaking.
• Corrected: She, along with my other group members, is speaking.

The words between the commas (along with my other group members) have confused the writer, so that the singular subject is now incorrectly paired with a plural verb (She . . . are). Regardless of how many words come between the subject and the verb, the two still have to agree, as in our corrected example (She . . . is).

Ask yourself: What is the primary subject and the primary verb of the sentence? Pair them in order (subject + verb) and remove any intervening words to see if subject and verb agree: Charlotte and her friends are on holiday. She is speaking.

For more on grammar, consult Maxine Ruvinsky’s helpful book Practical Grammar. You’ll also find our handouts on punctuation and sentence types useful in revising your writing for grammatical issues.