When to Use a Comma: Basic Rules For Students

April 25, 2019

In the age of digitalization and communicating through abbreviated messages, sound knowledge of punctuation is almost a superpower. Start from learning when to use a comma, the most frequently used mark. Rules can be tricky, and some exceptions can be difficult to remember. To make it all easier, you can come up with associations or notable examples from the best essay writing checker RobotDon. We decided to be the ones who help you with this.

What is a comma and why do we use it?

Let’s start from the basics. A comma is a punctuation mark that looks like a hook, which is used in writing to separate words, phrases, and clauses within a sentence. Its purpose is to designate intonation on paper. Comma punctuation helps to specify and deliver the meaning of a written message.

Why writers use these punctuation marks? Proper comma usage shapes a text, makes it clear, better structured, emotional. Sometimes writers break common rules and use punctuation in their own way, mostly in order to emphasize a particular part, to slow down or speed up particular events, to express tension, etc. Thus, it becomes another tool of expression.

When to use a comma in a sentence: 13 simple rules

#1. Use it to indicate a short pause in a sentence. Its placement is required between all objects/creatures mentioned in the sentence. It also divides parts of a sentence that deliver different messages.

Incorrect: Between a movie and a book I’ll choose a book.

Correct: Between a movie and a book, I’ll choose a book.

Tip: Read aloud what you’ve written to check whether there is a pause. Then read it closely again to make sure it looks logical.

#2. Use it after words however, therefore, moreover, furthermore. These and other introductory words should always be separated from the rest of the sentence, just like appositives that stand at the beginning.

Incorrect: Moreover you get the 7-day trial period.

Correct: Moreover, you get the 7-day trial period.

Tip: Always separate linking words from the rest of the sentence.

#3. Don’t put commas between two nouns in compound subjects or predicates, unless one of them is parenthetical. If words form a compound subject, they don’t come as listings. Even if one part is a long verb phrase, it shouldn’t be separated.

Incorrect: I bought a pair of jeans and a green jacket.

Correct: I bought a pair of jeans and a green jacket.

Tip: Check if these words have the same weight. If yes, they shouldn’t be separated.

#4. Use commas between multiple adjectives. Adjectives that relate to the same noun or modify the same object. However, there are nuances regarding when to put a comma between multiple adjectives. According to the Oxford Style Manual approach to grammar, adjectives are categorized as classifying and qualitative. Commas are required only between adjectives of the same category.

Incorrect: 1) He entered the room with bright colorful wallpapers. 2) It was a new, red car.

Correct: 1) He entered the room with bright, colorful wallpapers. 2) It was a new red car.

Tip: Use commas between adjectives that characterize common aspects or classes: color, feeling, material, etc., describe a feature from the same perspective.

#5. Divide two independent clauses with commas, if you want to join them in one sentence. There are dependent clauses that cannot stand on their own, even in case they contain subject and predicate. If these clauses start a sentence, they are separated.

Incorrect: It was a rainy evening we stayed at home.

Correct: It was a rainy evening, we stayed at home.

Tip: Check if both clauses make sense separately. If yes, put a comma there.

#6. Use commas within a comparison. Place it before “compared to,” “like how,” “just as,” and similar link phrases require this punctuation mark before them. Don’t use it before “than” in comparisons.

Incorrect: It was an easy task compared to our previous essay.

Correct: It was an easy task, compared to our previous essay.

Tip: Read what you’ve written to check if you make a pause before the conjunction. You don’t stop only before “than.”

#7. Separate a question from a statement by placing a comma between them. A question tag is featured not only in tail questions. Some words and phrases at the end of the statement turn it into question and encourage readers to answer.

Incorrect: You like this English movie right?

Correct: You like this English movie, right?

Tip: Commas mark the end of the statement instead of a dot.

#8. Highlight additional or non-essential information about a noun. It can be an explanation or specification of information, an offset negation, a shift that occurs in the sentence or thought process, a parenthetical element, etc. All these things are separated from the rest of the sentence according to comma rules.

Incorrect: My pets, especially chinchillas require a lot of care.

Correct: My pets, especially chinchillas, require a lot of care.

Tip: Everything that can be left out without changing the meaning is marked by commas from both sides.

#9. Put a comma to introduce or interrupt direct quotations that are shorter than three lines. This mark is always used when attributing short quotes, though its place depends on quote type. The comma goes outside quotation marks when attribution precedes the quote and goes inside quotation marks if it follows the quote.

Incorrect: He said “This is where we’ll go.” / “This is where we’ll go” he said.

Correct: He said, “This is where we’ll go.” / “This is where we’ll go,” he said.

Tip: Check if it looks nice and neat.

#10. Add this punctuation mark in direct addresses and dates. It separates each element in an address (street, city, state, zip code) and full date (weekday, month and day, year). Using commas is necessary after city-state combination and any date combination within a sentence.

Incorrect: 1) Deliver the package to 48 Madison Street New York NY. 2) It happened on sunny Tuesday May 25 2008.

Correct: 1) Deliver the package to 48 Madison Street, New York, NY. 2) It happened on sunny Tuesday, May 25, 2008.

Tip: Each part is a separate piece of information, micro-message that has its boundaries.

#11. Always place a comma before “but” in independent clauses. However, if “but” connects an independent clause with a dependent one, it is not necessary.

Incorrect: He was running fast but the bus left two minutes before the scheduled time.

Correct: He was running fast, but the bus left two minutes before the scheduled time.

Tip: If both parts make sense separately, divide them with a proper mark.

#12. Put a comma before “and” in case it links two independent clauses. Remember that two clauses of a compound sentence are always divided, no matter whether conjunctions are used or not.

Incorrect: It is my new apartment and I like it a lot.

Correct: It is my new apartment, and I like it a lot.

Tip: If both clauses sense separately, put a comma between them.

#13. Don’t forget about Oxford comma. It is used in listings before “and” that adds the last component in a sequence.

Incorrect: Clothes, toys, books and candy wrappers were scattered all over the room.

Correct: Clothes, toys, books, and candy wrappers were scattered all over the room.

Tip: Just divide all items on the list.

The most common comma mistakes in students’ essays

School, college, and university students tend to make similar errors in their essays. Punctuation is tricky sometimes. If you don’t know how to use commas in some specific cases and try to check a sentence using one of those you’ve learned, it is easy to make grammar mistakes or try our comma checker tool. We picked the rules for the most common cases observed in students essays.

  • Don’t put a comma before “because,” except the cases when a clause that contains it contradicts an explained clause.
  • Comma before “please” is required only in case it starts a dependent clause. Don’t use it after “please,” unless you want to express irritation.
  • When two or more separate adjectives appear before a noun, commas are appropriate in case they coordinate with one another.
  • If you can change the order of adjectives or place “and” between them without changing the sense, no need to put a comma there.
  • The sets of correlative conjunctions (either … or, neither … nor, both … and, not only … but, etc.) are not separated by commas.
  • A comma before “too” is needed in case it stands in the middle of the sentence; before “such as” is required in case it is a part of nonrestrictive clause (can be taken out without changing the meaning).
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