Using Commas (Grammar and Punctuation)
The Quick Answer
The Rules for Using CommasA comma is used:
- After setting the scene at the start of a sentence (e.g., Now I'm older, I understand. )
- After transitional phrases like However, Consequently, or As a result (e.g., As a result, I now understand. )
- After an interjection (e.g., Jeepers, now I understand. )
- Before a conjunction joining two independent clauses (e.g., I like cake, and I like cheese. )
- As parentheses (e.g., Janet and John Baxter, who live next door, adore cakes. )
- To separate list items (e.g., bread, milk, and cheese () / bread, milk and cheese () – more on this below.)
- After a long subject if it helps the reader (e.g., A, B, C, and D, are required to bake this cake. )
- In numbers (e.g., 3,213 )
- With the vocative case (e.g., I know your auntie, John. )
- Before a quotation (e.g., She said, "I understand." )
The Rules for Using CommasThis page explains when to use commas and gives examples for each type of comma usage.
Using Commas after "Setting the Scene"
It is quite common for a sentence to start with words which "set the scene." These words usually state a place, a time, a condition, or a fact before the main part of the sentence. Words that "set the scene" at the start of a sentence are usually followed by a comma. You do not have to use a comma; i.e., it is not a strict ruling. It's just a common style. However, as it will help your reader, it is a useful style to adopt. For example:
- In Paris, they simply stared when I spoke to them in French. (sets a place)
- At exactly 4 o'clock, two of the kidnappers re-entered the room. (sets a time)
- If you don't know where you are going, you will probably end up somewhere else. (Laurence J. Peter, 1919-1988) (sets a condition)
- As you were born here, it makes sense for my group to take the map. (states a fact)
- When a man tells you that he got rich through hard work , ask him "Whose?" (Don Marquis, 1878-1937) (sets a time)
- When I was a boy, I was told that anybody could become President. Now I'm beginning to believe it. (Clarence Darrow, 1857 - 1938) (First "scene setting" adverb – comma used. Second "scene setting" adverb – no comma required)
- Two of the kidnappers re-entered the room at exactly 4 o'clock.
- Two of the kidnappers, at exactly 4 o'clock, re-entered the room.
Using Commas after a Transitional Phrase
A transitional phrase is a term like However, Consequently, Therefore, and As a result. (There are others, but these are the most common.) A transitional phrase sits at the start of sentence and acts like a bridge to an idea in the previous sentence. A transitional phrase is usually followed by a comma. For example:
- John has eaten at least two cakes a day for the last decade. As a result, he has been placed in a high-risk group for diabetes.
- I think. Therefore, I am. Rene Descartes (1596-1650)
- All progress is initiated by challenging current conceptions, and executed by supplanting existing institutions. Consequently, the first condition of progress is the removal of censorships. George Bernard Shaw (1856-1950)
- Orthodox medicine has not found an answer to your complaint. However, luckily for you, I happen to be a quack.
Read more about using a comma after a transitional phrase.
Using Commas after an Interjection
An interjection is usually a short word inserted into a sentence to express an emotion or feeling. Expressions such as yes, phew, and indeed are examples of interjections. Often, an interjection will sit at the start of the sentence but not always. It is normal to offset an interjection with a comma (or commas if it's in the middle of the sentence). In the examples below, the interjections are shaded:
- Oh great, the boiler's broken down.
- Yes, that's three out of three.
- I understand your predicament, but, crikey, there is nothing we can do.
Read more about using a comma after an interjection.
Using Commas before a Conjunction
Words like and, or, and but are known as conjunctions. (There are other conjunctions, but these three are the most common.)
When a conjunction joins two standalone sentences (or independent clauses), it is usual to place a comma before it. For example (conjunctions shaded):
- Lee can sing, and he can dance (Here, the conjunction and is joining two standalone sentences: "Lee can sing." + "He can dance.")
- Lee can sing, and dance (Here, the conjunction and is not joining two standalone sentences. The words "and dance" are not a standalone sentence. This is just a list of things that Lee can do. This section is not about using commas in lists. That is covered below and in the lesson Using Commas in Lists.)
- No amount of time can erase the memory of a good cat, and no amount of masking tape can ever totally remove his fur from your couch. (Leo Buscaglia, 1925-1998)
- When you have got an elephant by the hind leg, and he is trying to run away, it's best to let him run. (Abraham Lincoln, 1809-1865) ("When you have got an elephant by the hind leg" is not a standalone sentence.)
Read about the Oxford Comma.
Using Commas for Parentheses
We all know that additional information (such as an explanation or an afterthought) can be offset with brackets. However, brackets are just one of the choices you have. You can also use commas or dashes. The information which is offset by commas, brackets, or dashes is called a parenthesis. The punctuation marks used to offset a parenthesis (i.e., dashes, brackets, or commas) are called parentheses.
Examples (with each example of parenthesis shaded):
- The case has, in some respects, been not entirely devoid of interest.
- At 4 o'clock yesterday, David Frost, a cleaner from the Lakes Estate, was charged with "dog napping" his former headmaster's poodle.
- Joanne Baxter, who originally appeared as a witness, has been found guilty of handling stolen goods. (Note: When a parenthesis starts with who or which (i.e., a relative pronoun), you should look to use commas as opposed to brackets or dashes. This is not a 100% rule, but commas are far more common when the parenthesis starts with a relative pronoun.)
Read more about using commas to replace brackets.
Using Commas in Lists
When writing a list in "sentence form" (i.e., not as bullet points), it is normal to separate the list items using commas. For example:
- Fish, chips, and peas
The first part of the rule is easy enough: when there are just two items in a list, there is no need to use a comma between them.
- Fish and chips
- The Bakerloo Line runs between Harrow and Wealdston, and Elephant and Castle.
- Fish, chips, and peas ()
- Fish, chips and peas ()
- Fish, chips, and peas () (This is correct if you're an advocate for the Oxford Comma.)
Read more about using commas in lists.
Using Commas after a Long Subject
When the subject of a sentence is made up of lots of elements, it is known as a compound subject. For example:
- Janet is popular. (This is a normal subject (i.e., not a compound one). The subject has one element: Janet.)
- Janet and John are popular. (This is a compound subject because it has two elements: Janet and John.)
- The large gorilla is popular. (This is a normal subject. It has one element: The large gorilla.)
- The large gorilla with the bright blue eyes and the albino lion cub with piercing pink eyes are popular. (This is a compound subject with two elements.)
- Leaving a list of internet passwords, increasing your life insurance, and writing a will, will give you peace of mind while you are on operations. (Here, the writer has used a comma after will to show the end of the subject. It is hard to argue that this comma does not help the reader.)
Using Commas with Numbers
Commas can be used every 3 decimal places in large numbers to make them more readable. For example:
- 3.356 (in Europe)
- 184.108.40.2066 (in Europe)
- 175.757,01 (in Europe)
Using Commas before Speech Marks
Words like He said, She shouted, The author stated, and She wrote often precede a quotation. A comma can be used after these words to separate them from the quotation. For example:
- He said jokingly, "The world is my lobster."
- Paul whispered, "Is he always that miserable?"
In fact, it's your choice whether you follow your introductory words with a comma, a colon, or nothing. It depends on your desired flow of text. If you don't really care about the desired flow of text and you'd like some guidelines to help you decide which to use, then there is a useful guideline which states that a comma should be used for short quotations (six words or fewer) and colon should be used for longer quotations. (This is not a rule. It's a useful guideline.)
Read more about using a comma before speech marks.
Using Commas with the Vocative Case
When words are used to address somebody (or something) directly, those words are said to be in the vocative case. In English, the vocative case is shown by offsetting it from the rest of the sentence with a comma (or commas if it's in the middle of the sentence). In the examples below, the words in the vocative case are shaded:
- Do me the courtesy of shutting up, Alan.
- Darling, can you take the casserole out the oven?
- I know your sister, Jason.
- Tell me it's good news, doctor.
- And that, your Majesty, is how you make Eccles Cakes. I mean, it's how one makes Eccles Cakes.