Grammar Rules Library
Learn about common grammar rules, style guidelines, and clarity improvements to enhance your writing.
Subject-Verb Agreement
The subject and verb in a sentence must agree in number. Singular subjects take singular verbs, and plural subjects take plural verbs.
Examples
Incorrect:
The team are playing well.
Correct:
The team is playing well.
Incorrect:
She don't like coffee.
Correct:
She doesn't like coffee.
Tips
- Collective nouns (team, group, family) usually take singular verbs
- Check if the subject is singular or plural before choosing the verb form
- Don't be confused by phrases between the subject and verb
Comma Splice
A comma splice occurs when two independent clauses are joined with only a comma. Use a semicolon, conjunction, or separate sentences instead.
Examples
Incorrect:
I love writing, it's my passion.
Correct:
I love writing; it's my passion.
Incorrect:
She studied hard, she passed the exam.
Correct:
She studied hard, and she passed the exam.
Tips
- Use a semicolon to join closely related independent clauses
- Add a coordinating conjunction (and, but, or, so) after the comma
- Split into two separate sentences if the ideas are distinct
Sentence Fragment
A sentence fragment is an incomplete sentence missing a subject, verb, or complete thought. Every sentence needs both a subject and a predicate.
Examples
Incorrect:
Because I was tired.
Correct:
I went to bed early because I was tired.
Incorrect:
Running through the park.
Correct:
She was running through the park.
Tips
- Ensure every sentence has a subject and a verb
- Complete dependent clauses by adding an independent clause
- Read your sentence aloud to check if it expresses a complete thought
Passive Voice
Passive voice can make writing less direct and harder to read. Active voice is usually clearer and more engaging.
Examples
Incorrect:
The report was written by Sarah.
Correct:
Sarah wrote the report.
Incorrect:
Mistakes were made during the process.
Correct:
We made mistakes during the process.
Tips
- Identify who or what is performing the action
- Move the actor to the subject position
- Passive voice is acceptable in scientific writing or when the actor is unknown
Wordiness / Redundancy
Using more words than necessary makes writing unclear and tiring to read. Aim for concise, direct language.
Examples
Incorrect:
Due to the fact that it was raining, we stayed inside.
Correct:
Because it was raining, we stayed inside.
Incorrect:
In order to succeed, you must work hard.
Correct:
To succeed, you must work hard.
Tips
- Replace wordy phrases with simpler alternatives
- Eliminate redundant words that don't add meaning
- Use strong verbs instead of verb + noun combinations
Unclear Pronoun Reference
Pronouns must clearly refer to a specific noun. Ambiguous pronouns confuse readers about who or what you're discussing.
Examples
Incorrect:
John told Mike that he needed to leave.
Correct:
John told Mike, "You need to leave."
Incorrect:
When the car hit the tree, it was damaged.
Correct:
When the car hit the tree, the car was damaged.
Tips
- Ensure each pronoun has a clear antecedent
- Repeat the noun if the pronoun reference is ambiguous
- Rewrite the sentence to eliminate confusion
Apostrophe Misuse
Apostrophes show possession or contraction, not plurality. Don't use apostrophes to make nouns plural.
Examples
Incorrect:
The cat's are sleeping.
Correct:
The cats are sleeping.
Incorrect:
Its a beautiful day.
Correct:
It's a beautiful day.
Tips
- Use apostrophes for possession (Sarah's book)
- Use apostrophes for contractions (it's = it is)
- Never use apostrophes for plural nouns
Run-on Sentence
Run-on sentences contain two or more independent clauses without proper punctuation or conjunctions.
Examples
Incorrect:
I love reading I read every day.
Correct:
I love reading. I read every day.
Incorrect:
She finished her homework then she went outside.
Correct:
She finished her homework, and then she went outside.
Tips
- Use a period to separate independent clauses
- Use a semicolon for closely related ideas
- Add a comma and coordinating conjunction
Their / There / They're
These three words sound the same but have different meanings and uses. "Their" shows possession, "there" refers to a place, and "they're" is a contraction of "they are".
Examples
Incorrect:
Their going to the store over they're.
Correct:
They're going to the store over there.
Incorrect:
The students put there books on the desk.
Correct:
The students put their books on the desk.
Tips
- Their = belongs to them (possessive)
- There = a place or position
- They're = they are (contraction)
Your / You're
"Your" is possessive (belongs to you), while "you're" is a contraction meaning "you are". These are commonly confused.
Examples
Incorrect:
Your going to love this movie.
Correct:
You're going to love this movie.
Incorrect:
Is this you're book?
Correct:
Is this your book?
Tips
- Your = belongs to you (possessive)
- You're = you are (contraction)
- Test by replacing with "you are" - if it works, use "you're"
Its / It's
"Its" is possessive (belongs to it), while "it's" is a contraction meaning "it is" or "it has". Note that possessive pronouns don't use apostrophes.
Examples
Incorrect:
The dog wagged it's tail.
Correct:
The dog wagged its tail.
Incorrect:
Its a wonderful day outside.
Correct:
It's a wonderful day outside.
Tips
- Its = belongs to it (possessive)
- It's = it is or it has (contraction)
- Test by replacing with "it is" - if it works, use "it's"
Affect / Effect
"Affect" is usually a verb meaning to influence, while "effect" is usually a noun meaning a result or outcome.
Examples
Incorrect:
The weather will effect our plans.
Correct:
The weather will affect our plans.
Incorrect:
The medication had a positive affect.
Correct:
The medication had a positive effect.
Tips
- Affect = verb (to influence)
- Effect = noun (the result)
- Remember: Affect is an Action, Effect is an End result
Then / Than
"Then" relates to time (what happens next), while "than" is used for comparisons.
Examples
Incorrect:
First we ate dinner, than we watched a movie.
Correct:
First we ate dinner, then we watched a movie.
Incorrect:
She is taller then her brother.
Correct:
She is taller than her brother.
Tips
- Then = relates to time (what happens next)
- Than = used for comparisons
- Remember: ComparisON uses thaN
Dangling Modifier
A dangling modifier is a phrase that doesn't clearly modify any word in the sentence, creating confusion about what or who is being described.
Examples
Incorrect:
Walking to the store, the rain started pouring.
Correct:
While I was walking to the store, the rain started pouring.
Incorrect:
After finishing the assignment, the TV was turned on.
Correct:
After finishing the assignment, I turned on the TV.
Tips
- Place the modifier next to the word it modifies
- Ensure the subject performing the action is clear
- Rewrite the sentence to eliminate ambiguity
Misplaced Modifier
A misplaced modifier is placed too far from the word it modifies, causing confusion or unintended humor.
Examples
Incorrect:
She served sandwiches to the children on paper plates.
Correct:
She served sandwiches on paper plates to the children.
Incorrect:
I saw a stray dog riding my bike.
Correct:
While riding my bike, I saw a stray dog.
Tips
- Place modifiers as close as possible to what they modify
- Read your sentence aloud to catch awkward placements
- Consider if the modifier could be misinterpreted
Parallel Structure
Items in a list or series should use the same grammatical form. This creates rhythm and makes writing easier to read.
Examples
Incorrect:
She likes hiking, to swim, and riding bikes.
Correct:
She likes hiking, swimming, and riding bikes.
Incorrect:
The job requires attention to detail, being organized, and you must communicate well.
Correct:
The job requires attention to detail, organization, and communication skills.
Tips
- Keep verb forms consistent in lists
- Maintain the same structure for items in a series
- Check that all list items start with the same part of speech
Who / Whom
"Who" is used as a subject (does the action), while "whom" is used as an object (receives the action).
Examples
Incorrect:
Whom is coming to dinner?
Correct:
Who is coming to dinner?
Incorrect:
To who should I address this letter?
Correct:
To whom should I address this letter?
Tips
- Who = subject (does the action)
- Whom = object (receives the action)
- Test by replacing with he/him: "he" → who, "him" → whom
That / Which
Use "that" for essential clauses (restrictive) without commas. Use "which" for non-essential clauses (non-restrictive) with commas.
Examples
Incorrect:
The car which is parked outside is mine.
Correct:
The car that is parked outside is mine.
Incorrect:
My car, that is blue, needs repairs.
Correct:
My car, which is blue, needs repairs.
Tips
- That = essential information (no commas)
- Which = extra information (use commas)
- If you can remove the clause without changing meaning, use "which"
Split Infinitive
A split infinitive occurs when an adverb is placed between "to" and the verb. While sometimes acceptable, it can often be reworded for clarity.
Examples
Incorrect:
She decided to quickly run to the store.
Correct:
She decided to run quickly to the store.
Incorrect:
We need to carefully consider all options.
Correct:
We need to consider all options carefully.
Tips
- Place the adverb before or after the infinitive
- Split infinitives are acceptable in modern English when natural
- Avoid splits when they make sentences awkward
Double Negative
Using two negative words in the same clause creates a double negative, which is grammatically incorrect and confusing in standard English.
Examples
Incorrect:
I don't have no money.
Correct:
I don't have any money.
Incorrect:
She can't hardly wait for the concert.
Correct:
She can hardly wait for the concert.
Tips
- Use only one negative word per clause
- Replace "no" with "any" after a negative verb
- Remove "hardly," "barely," "scarcely" when using "can't"