In 2018, a company in Portland, Maine settled a court case for $5m because of a missing comma after three lorry drivers for Oakhurst Dairy claimed that they were owed years of unpaid overtime. The state’s laws declared that overtime wasn’t due for workers involved in “the canning, processing, preserving, freezing, drying, marketing, storing, packing for shipment or distribution of: 1) agricultural produce; 2) meat and fish products; and 3) perishable foods”.
The drivers managed to successfully argue that because there was no comma after “shipment” and before “or distribution”, they were owed overtime pay. If a comma had been there, the law would have explicitly ruled out those who distribute perishable foods.
It is helpful to know about dependent and independent clauses when deciding whether to use a comma. An independent clause contains a subject, a verb, and it conveys a complete thought – it could be a complete sentence on its own. A dependent clause contains a subject and a verb, but it does not convey a complete thought.
David practiced his golf on Saturday.
After David practiced his golf on Saturday
Adding certain words to an independent clause can change it to a dependent one. For example, after in the clause above. Other words that do this include Although, As, Because, Before, Even if, Since, Though, Unless, Until, Whatever, When, Whether, and While.
If two independent clauses are joined in a sentence using and, but, for, nor, or, so, yet (the seven coordinating conjunctions), then a comma must be used before the conjunction. For example,
David practiced his golf on Saturday, so he would become a better player.
A comma is used between the clauses when the dependent clause comes first. For example,
Whenever David practiced his golf, he improved his game.
David improved his game whenever he practiced his golf.
A common error is the use of a comma on its own, between two independent clauses. For example,
There were six people watching the game, all of them enjoyed it.
The above is wrong and is an example of a comma splice. Such comma splices can be fixed in various ways:
There were six people watching the game. All of them enjoyed it.
There were six people watching the game; all of them enjoyed it.
There is more on semi-colons here.
There were six people watching the game, and all of them enjoyed it.
Another common error is to join two independent clauses without any punctuation. For example,
My sister is a very competent doctor she is very highly regarded in her profession.
The above is wrong and is an example of a run-on sentence. This error can be fixed in ways similar to the comma splice correction:
My sister is a very competent doctor. She is very highly regarded in her profession.
My sister is a very competent doctor; she is very highly regarded in her profession.
My sister is a very competent doctor, and she is very highly regarded in her profession.
An essential clause, as the name suggests, changes the meaning or emphasis of a sentence and does not require to be separated by commas. For example,
The children from that school who were from low-income households achieved the highest marks.
A non-essential clause embedded within an independent clause should be separated by commas. For example,
The children from that school, including those from low-income households, achieved the highest marks.
Non-essential words, phrases, and clauses can be identified by considering whether the sentence retains its meaning and grammatical sense upon their removal. i.e. does the sentence still make the same sense without them. For example,
The man dancing alone looked out of place. [Essential]
The dog who bit you is owned by my cousin. [Essential]
The number of people, however, continues to fall. [Non-essential]
My last job, which I really loved, only lasted for two years. [Non-essential]
Conjunctions are words, or groups of words that connects words, phrases, or clauses. There are different types of conjunctions.
Three or more words, phrases, or clauses written in a series should each be separated by a comma. For example,
Jack was ready to play some hockey now that he had his helmet, stick, and shin guards.
Sam was instructed to skate faster, shoot lower, and hit harder when on the ice.
If two or more adjectives describe a noun they are separated by a comma if they are of equal importance. A useful test for this is to ask whether they can be written in reverse order and separated with an “and”. If they can, they should be separated by a comma. For example,
We enjoyed a relaxed, peaceful holiday in France.
It seems like it is always the blond, blue-eyed babies that win these competitions.
The new racing bike was the perfect gift.
The town was cut off after the severe winter storm.
Footnote: It is becoming more common for writers to omit a comma between adjectives especially when the meaning remains the same.
Commas are used to separate days of the month, months within a year, and the year itself. For example,
Francis was born on the 25th July, 1958, on a bright sunny day.
Addresses and place names and their associated regions are separated by commas. For example,
Banff, Alberta is a Canadian town named after Banff, Scotland.
Please send all correspondence to The White House, 1600 Pennsylvania Avenue NW, Washington, DC 20500.
Larger numbers written in word form require commas to separate the thousands and millions (and so on) places. For example,
The number 2,945,301 is written in words as two million, nine hundred and* forty-five thousand, three hundred and* one.
*Note: North American English writers do not include the “and” when writing numbers.
Use a comma before a quotation with a sentence. For example,
The coach stated that, “I think that was the best game the team has played all season.”
It is challenging to remember all the rules and guidance on when and when not to use commas. Read your writing out loud and listen for the slight pauses and changes of intonation; these often happen where commas should be.