Teaching grammar basics: using commas

By Oliver Shrouder

23 Nov 2022

A teacher at the front of the classroom talking to students.

What are commas?

A comma (,) is a punctuation mark that is used to show where a text divides. This divide can be caused by phrases, clauses, or conjunctions. Commas are also used when writing lists, as they can clarify each item or number.


There are many ways to use a comma, and the most common use of the comma is to separate items in a list:

  • Fish, chips and mushy peas.
  • I invited my friends Darren, Ella and James.
  • For breakfast I had cereal, a banana and a coffee.

In each of these sentences, commas are used to separate words and word groups to make each list as clear as possible. These lists can be more detailed than words, too. You can use commas in this way to list a series of phrases or a series of clauses:

  • The teacher looked in the top drawer, through her bag, and around the classroom for the missing sheets.

Though the things being listed are more complicated than fish and chips, the comma is used in the same way to differentiate each item.

Commas to clarify meaning

One element of punctuation that may confuse students is the use of the Oxford comma, which has been used in only one of the lists so far:

  • Bananas, oranges, and apples.
  • Bananas, oranges and apples.

Both sentences are grammatically correct, but the first uses an Oxford comma. The Oxford comma is used to separate the last item in a sentence, and usually appears just before the last “and”. This comma is placed here to clarify meaning.

  • My favourite people are my parents, the prime minister, and Beyoncé.
  • My favourite people are my parents, the prime minister and Beyoncé.

Naturally, your parents are not the prime minister or Beyoncé; the Oxford comma allows the sentence to be as clearly worded as possible.

Independent clauses

The use of the comma is not exclusive to lists. Take the sentences below:

  • You can come shopping with me, or you can stay at home.
  • My friend loves playing the piano, and he loves classical music.

The sentences above use commas to join two independent clauses into one sentence. An independent clause is a complete idea, and using the comma relates one clause to another. The person could go shopping. The person could also stay at home. These phrases make sense on their own, but the comma and conjunction (words such as “and”, “or”, and “but”) allow a reader to know what each sentence refers to.

In the second sentence, the use of “he” becomes confusing, as we are not certain who the pronoun belongs to. Using commas to join clauses makes the sentences much easier to understand, as the “he” must refer to the friend. Otherwise, the “he” could be anyone. However, remember that you must use a comma and a conjunction together in these sentences, or you will end up with something known as a comma splice, where a comma is used to separate two independent clauses without a conjunction.

  • Incorrect: Sara went to the park, she brought her dog with her.
  • Correct: Sara went to the park, and she brought her dog with her.

Subordinate clauses

A comma can also be used after a subordinate clause to provide information:

  • After I came back home, Dad put the shopping away.
  • However, Dad was annoyed he had to do it on his own.

These two sentences are related in their use of commas, though their use is slightly different. In the first sentence, an introductory phrase is indicated by the comma; this tells the reader that the main part of the sentence is about to begin.

Similarly, the second sentence shows that a comma can be used after an introductory word. This word is also called a “transitional phrase”, as it transitions the previous sentence into the next. Some examples of these words are “therefore”, “consequently”, and “as a result”.


Another way to use commas is to represent parenthesis. Parentheses, in English, are used to insert extra information or thoughts into a sentence. This information is always surrounded by punctuation marks:

  • His favourite football team, whom he has loved since he was young, just won the championship!

The commas in this sentence indicate the extra information in the sentence. We know that this is a parenthetical phrase as, if we took out the additional information, the sentence still makes sense:

  • His favourite football team just won the championship!

The information about the speaker’s youth is not necessary to understand the complete sentence, but adding this extra detail can help a reader understand the person better and provide more depth.

Common comma mistakes

Too many commas

Frankly, a sentence with many, many commas is, well, pretty difficult to understand, and, even if the commas are used correctly, can confuse the reader.

It’s important to remember the purpose of grammar when constructing a sentence. Ultimately, commas are designed to help readers understand a sentence. They clarify meaning, separate clauses and help a reader understand the point of a sentence. Used incorrectly, the sentence doesn’t make sense. Too many commas can make a sentence stodgy and difficult to read.

But using too many commas in a sentence is a common mistake learners make. When speaking aloud, it can be difficult to tell where commas sit naturally.

This can result, in learners using commas, in very, strange places.

To combat this common mistake, make sure the methods you use to teach commas are consistent and structured. Learners should avoid using commas “where they should take a breath”, and instead understand that commas have specific rules; understanding these rules can lead to improved reading comprehension. This can be achieved through an explicit grammar instruction strategy, either in the classroom or through digital curricula like Bedrock’s grammar curriculum.

No comma in a compound sentence

In a compound sentence, the conjunction is always preceded by a comma. For example:

  • Julie went to bed early, for she was exhausted.
  • Noah tied his shoelaces, but they were undone again in no time.
  • Dad said yes, yet Mum said no.

However, when we speak naturally, it’s not easy to detect where this comma might sit. This leads to learners writing compound sentences without commas.

A simple way to target this is to help learners recognise the presence of conjunctions. Some teachers use the acronym of FANBOYS:

  • For
  • And
  • Nor
  • But
  • Or
  • Yet
  • So

Teaching learners to recognise chunks of a sentence as “conjunctions”, “nouns” or “clauses” encourages them to think analytically about how a sentence is constructed, helping them to become more deliberate in the way they transcribe. This leads to fewer mistakes when adding commas to conjunctions.

The Comma Splice... or when a comma separates two independent clauses

he most notorious mistake you can make when using commas is a comma splice - and it is one of the most common. Many UK adults continue to splice their commas throughout their lives.

As this mistake is so common, it’s important to target it explicitly by reinforcing the idea of independent clauses.

  • Hamburgers do not have to contain meat, some can be vegan.

When we split this sentence, we have two independent clauses: “Hamburgers do not have to contain meat” and “some can be vegan”.

The comma used in the sentence above is incorrect, as it is splicing together two independent clauses.

To fix this, the writer can choose between three options:

  • Adding a semicolon
    • Hamburgers do not have to contain meat; some can be vegan.
  • Separating the sentences
    • Hamburgers do not have to contain meat. Some can be vegan.
  • Using a conjunction (and a comma!)
    • Hamburgers do not have to contain meat, as some can be vegan.

Conjunctions, comma splices and comma overuse are just some of the common grammar mistakes learners make. Learn about the most frequent errors used in grammar lessons to anticipate common misconceptions.

The UK's #1 literacy solution

Ensure every learner understands the grammar they need to thrive.