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Sentences and Grammar

Using Commas in Sentences

There are four rules for using commas in sentences.


1. Use a comma after introductory words or phrases


  • Annoyed, the manager stomped back into the storeroom.
  • Expecting the worst, we liquidated most of our inventory.
  • While we were eating lunch, an important fax came.

Tip: The part of the sentence after the comma should be a complete thought.


2. Use a comma before and after "internal sentence interrupters"

An "internal sentence interrupter" is a word, phrase, or clause that significantly breaks the flow of a sentence.


  • New Orleans, home of the Saints, is one of my favourite cities.
  • Megabyte, a word unheard of a decade ago, is very common today.
  • Mrs. McCord, the investment specialist, left a message for you.

Tip: If you can take the phrase out, and the sentence will still make sense, the phrase should have commas before and after it.


3. Use a comma to separate two complete thoughts joined by a conjunction

A conjunction is a word used to connect clauses or sentences, or to coordinate words in the same clause, for example, and, but, and if.


  • I went to bed early last night, so I feel rested this morning.
  • Susan worked through lunch, and now she is able to leave early.

Tip: If the words after the conjunction do not form a complete thought, don’t use a comma before the conjunction.


4. Use commas to separate
a. Three or more items in a series
b. Dates, addresses, geographical names, academic degrees, and long numbers

  • The old Tempo’s engine squealed loudly, shook violently, and stopped.
  • The carpenter repaired the floor with dark, aged, oak flooring.
  • September 20, 1974, is her birth date.
  • I like the book 20,000 Leagues Under the Sea, by Jules Verne.
  • I went to visit Andrew Pearson, Ph.D., at the Royal Ontario Museum in Toronto, Ontario.

Tip: If the words after the conjunction do not form a complete thought, don’t use a comma before the conjunction.

When to Use Commas

When to Use Commas
When to Use Examples
When listing items in succession Pack an extra swimsuit, a towel, sunglasses, sunscreen, three bottles of water, lip balm, and an umbrella.
Do you want eggs, bacon, and toast or pancakes, fruit, and sausage?
Between multiple adjectives that are modifying the same noun The friendly, eager to please puppy.
The cold, windy Chicago weather
Before conjunctions linking independent clauses I want to go to bed, but I still have to finish this essay.
There are snakes in our garden, so I try to avoid going out there after dark.
After introductory words or phrases After dinner, make sure you wash the dishes.
When traveling, do not pack more than three ounces of liquid in your carryon.
Sure, it sounds like a good idea to me.
Well, I think we should probably ask Steven before we make plans.
Around nonessential clarifying phrases Grace Kelly, one of the most beautiful women in the world, married Prince Rainier of Monaco.
I hope The Hobbit, which was directed by Peter Jackson, is just as good as the Lord of the Rings movies were.
With dates and addresses His birthday is July 21, 1988.
I hear New Orleans, Louisiana has amazing food.
When directly addressing someone Mary, can you go to the store and pick up some milk?
I'd like you, Jake, to bring a dessert to the potluck.
At the salutation and close of a letter Dear Tom,

Common Sentence Errors


There are three very common errors that people make when writing sentences. If you can learn to identify and avoid these errors, your writing will improve right away!


Top Tips for Common Sentence Errors

1. Fragment
  • Part of a sentence that can’t stand alone and make sense
  • Often begins with words like since, although, except, such as, etc.

Error: Which is why I think that weekends should be four days long.

Correction: I think weekends should be four days long.

Repair Options:
  • Connect the fragment to the sentence before it, usually with a comma
  • Rewrite the fragment so that it can stand on its own and make sense
2. Run-On or Fused Sentence
  • Two complete thoughts stuck together without any punctuation

Error: I am going to a show tonight my friends are coming with me

Correction: I am going to a show tonight, and my friends are coming with me

Repair Options:
  • Add a comma and coordinating conjunction (and, or, nor, but, yet, so) after the first thought
  • Split the sentence into two, using a period and a capital letter
  • Separate the first and second complete thoughts with a semicolon
3. Comma Splice
  • Two complete thoughts joined with a comma

Error: The dog went to the park, he played fetch with his owner

Correction: The dog went to the park, and he played fetch with his owner

Repair Options:
  • Add a coordinating conjunction (and, or, nor, but, yet, so) after the comma
  • Replace the comma with a period and change the next letter to a capital
  • Use a semicolon to separate the two complete thoughts

Misused Spellings


Accept means "take." It is always a verb. Except means "excluding."

Everyone except Brian accepted my explanation.


The difference in pronunciation makes the difference in meaning clear. Advise (sounds like wise) is a verb. Advice (sounds like nice) is a noun.

I advise you not to listen to free advice.


Affect is a verb meaning "influence." Effect is a noun meaning "result." If you can substitute result, then effect is the word you need.

Learning about the effects of caffeine affected my coffee-drinking.

A lot

A lot (often misspelled alot) means "many" or "much," and should be avoided in academic writing. Use many or much instead. Allot means "distribute" or "assign."

He still has "a lot of" (many) problems, but he’s coping "a lot" (much) better. The teacher will allot each of the different questions to students.


Are is a verb. Our shows ownership.

Pierre Burton and Margaret Atwood are two of Canada’s best known writers. Canada is our home and native land


Pronunciation gives the clue here. Choose means to "select" in the present or future. Chose means that it was "selected" In the past

Please choose a topic. I chose film-making.


Coarse means "rough, unrefined." Sandpaper is coarse. Metaphorically, language full of profanities can be described as coarse. For all other meanings, use course.

That sandpaper is too coarse to use on a lacquer finish. You'll enjoy the photography course. Of course you'll come with us.


A complement completes something. A compliment is a gift of praise.

A glass of wine would be the perfect complement to the meal. Some people are embarrassed by compliments.


Your conscience is your sense of right and wrong. Conscious means "aware" or "awake" (able to feel and think).

After Ann cheated on the test, her conscience bothered her. Ann was conscious of having done wrong. The injured man was unconscious.


A Consul is a government official stationed in another country. A council is an assembly or official group. Members of council are councilors. Counsel can be used to mean both "advice" and "to advise."

The Canadian Consul in Venice was very helpful. The Women's Advisory Council meets next month. Maria gave me good counsel. She counselled me to hire a lawyer


A desert is a dry, barren place. As a verb, desert means "to leave behind." Dessert is the part of a meal you’d probably like two helpings of, so give it two s's.

The tundra is Canada's only desert region. As soon as our backs are turned, our lookout deserted his post. Jell-O is the children’s favourite dessert.


You'll spell dining correctly if you remember the phrase "wining and dining." Dinning means "making a loud noise."

The dog is not supposed to be in the dining room. We are dining out tonight. The sounds of the karaoke bar were dinning in my ears.


Pronunciation provides the clue. Does is an action (verb). Dose refers to a quantity of medicine.

Joseph does drive fast, doesn’t he? My grandmother used to give me a dose of cod liver oil every spring.


Forth means "forward." Fourth contains the number four, which gives it its meaning.

Please stop racing back and forth. The Raptors lost their fourth game in a row


Hear is what you do with your ears. Here is used for all other meanings.

Now hear this! Ranjan isn’t here. Here is your assignment


It's is a shortened form of it is. The apostrophe takes the place of the I in is. If you can substitute it is, then it's is the form you need. If you can't substitute it is, then its is the correct word.

It's really not difficult. (It is really not difficult). The book has lost its cover. (The book has lost it is cover makes no sense, so you need its). It's is also commonly used as the shortened form of it has. In this case, the apostrophe takes the place of the h and the a. It's been a bad month for software sales.


Later refers to time and has the word late in it. Latter means "the second of the two" and has two t's. It is the opposite of the former.

It is later than you think. You take the former, and I’ll take the latter.

Led (Lead)

The word lead is pronounced "led" only when it refers to the heavy, soft, grey metal used in items such as lead bullets or leaded windows. Otherwise, lead is pronounced to rhyme with "speed" and is used as the present tense of the verb to lead. (Led is the past tense of the same verb).

When I asked her to lead me to the person in charge, she led me to the secretary. Your suitcase is heavy; it must be filled with either gold or lead.


Pronunciation is the key to these words. Loose means "not tight." Lose means "misplace" or "be defeated."

A loose electrical connection is dangerous. Some are born to win, some to lose.


A miner works in a mine. Minor means "lesser" or "not important." For example, a minor is a person of less than legal age.

Liquor can be served to miners, but not if they're minors. For some people, spelling is a minor problem.


Again, pronunciation provides the clue you need. Moral refers to the understanding of what is right and wrong. Morale refers to the spirit or mental condition of a person or group.

Parents are responsible for teaching their children moral behaviour. The low morale of our employees is the reason for their high absenteeism.


Peace is what we want on earth. Piece means a part or portion of something, as in a "piece of pie."

Everyone hopes for peace in the Middle East. A piece of the puzzle is missing.


Personal means "private." Personnel refers to the group of people working for a particular employer or to the office responsible for maintaining employees' records.

The letter was marked "Personal and Confidential." We are fortunate in having highly qualified personnel. Yasmin works in the Personnel Office


Principal means "main." Principle is a rule.

A principal is the main administrator of a school. A federal government is Summerside's principal employer. The principal and the interest totaled more than I could pay (In this case the Principal is the main amount of money). One of our instructor's principles is to refuse to accept late assignments.


Quiet refers to a low level of sound; quite refers to the extent of something.

The chairperson asked us to be quiet. We had not quite finished our assignment.


Stationary means "fixed in place." Stationery is writing paper.

Did you want a laptop or stationary computer? Please order a supply of stationery.


Than is used in comparisons. Then refers to time.

Karim is a better speller than Ray. He made his decision then. Tanya withdrew from the competition; then she realized the consequences.


Their indicates ownership. There points out something or indicates place, and includes within it the word here (which also indicates place). I'm over here, you’re over there. They're is a shortened form of they are.

It was their fault. There are two weeks left in the term. Let’s walk over there. They're late, as usual.


The too with an extra o in it means "more than enough" or "also." Two is the number after one. For all other meanings, use to

She thinks she's been working too hard. He thinks so, too. There are two sides to every argument. The two women knew too much about each other to be friends.


Were is a verb. Where indicates place. We're is a shortened form of we are.

You were joking, weren't you? Where did you want to meet? We're on our way.


Who's is a shortened form of who is or who has. Otherwise, use whose.

Who's coming to dinner? (Who is coming to dinner?) Who's been sleeping in my bed? (Who has been sleeping in my bed?) Whose paper is this? ("Who is paper" makes no sense, so you need whose).


Woman is the singular form; compare man. Women is the plural form; compare men. Womyn is a different spelling of the word "Women" used by some to avoid using the suffix "men".

One woman has responded to our ad. The affirmative action policy promotes equality between women and men. Womyn deserve equal rights


You're is a shortened form of you are. If you can substitute you are for the you're in your sentence, then you're using the correct form. If you can't substitute you are, use your.

You're welcome. (You are welcome.) Unfortunately, your hamburger got burned. ("You are hamburger" makes no sense, so your is the word you want.)

Using Semi-Colons and Colons


A semi-colon can only separate two complete thoughts
  1. Use a semicolon instead of a coordinating conjunction* to contrast or expand related ideas.
    • Some students accepted their low marks quietly; others complained about them to their teacher.
    • Three doctors began the research project; only one completed it.
  2. Use a semicolon with a conjunctive adverb.**
    • Sales were good; however, expense continued to be high
    • She received her notes for the exam late; consequently, her grade was not very high
  3. In a list with commas in it already.
    • The student affairs committee is arranging trips to Whistler, B.C.; Banff, Alberta; and Halifax, Nova Scotia


A colon can be used only after a complete thought
  1. Before a list.
    • These people were in a play: Bill, Natasha, Tom, and Shelley
  2. Before an explanation.
    • The United Nations failed in its mission for one reason: It did not react strongly
    • Brent shouted and waved his arms: He had just set a new world’s record
  3. To introduce a quotation.
    • Hamlet put it best: "To be or not to be, that is the question."

*Coordinating Conjunctions = and, or, nor, but, yet, so

**Conjunctive Adverbs include furthermore, hence, thus, in addition

Subject Verb Agreement

A sentence needs a subject and a verb to be complete. A common error in college-level writing is the use of a subject and a verb that do not agree. Here are some rules to help you.


A noun or pronoun that tells you who/what the sentence is about. The subject performs the verb.

Example: We ran to catch the bus,
  The student is in the library.

A word that shows action (run, eat, study) or a state of being (is, am, are, was, were, etc.).

Example: We ran to catch the bus.
  The student is in the library.
Basic Principle:

Singular subjects need singular verbs; plural subjects need plural verbs.

Example (singular): Sam is a student at Georgian College.
NOT: Sam are a student at Georgian College
Example (plural): The students have classes every day this week.
NOT: The students has classes every day this week.

Collective nouns (i.e., group, people, family, team, etc.)

Collective nouns are words for single things that are made up of more than one person, animal, place, thing, or idea. For instance, many individuals compose a team, or many cows are referred to as a herd. These are singular subjects and thus require a singular verb agreement

Example: The band is on tour.
  A herd of sheep is grazing in the field.
  A shoal is swimming in the ocean.

Transitional Expressions

Transitional expressions build coherence in writing. Paragraphs are coherent (or "hang together") when ideas within them are linked, and one idea leads logically to the next.

Transitional expressions improve your writing. They show relationships and help create a logical flow of ideas. They help readers anticipate what's coming, reduce uncertainty, and speed up comprehension. They act as "road signs" to signal that a train of thought is moving forward, being developed, possibly detouring, or ending.

As the table below shows, transitions can add and strengthen, show cause and effect, indicate time or order, clarify, contradict, and contrast ideas. You must be careful to select the best transition for your purpose. Remember that coherence in written communication rarely happens without effort and skill.

To Add To Show Time
or Order
To Clarify To Show
Cause and
To Contradict To Contrast
As well as
In conclusion
For example
For instance
I mean
In other words
That is
This means
To put it another way
Simply put
As a result
For this reason
Under the circumstances
In fact
As opposed to
At the same time
By contrast
On the contrary
On the other hand
This being said

Note the transitions used in the following example:

Sequence: After he receives the figures, Ned will compile the report.

To clarify: The shops are getting busy already; for example, Wal-Mart was crazy yesterday.

Conclusion: Therefore, in recognition of your hard work, we are awarding you two days off with pay.