The English language is home to oodles of punctuation marks. But, the comma is arguably the most controversially used. For understandable reasons too. Since there are many rules guiding its use, with subtle factors determining when it's proper to use them or not, it's only normal to vacillate a bit when deciding if a comma is right for your string of words. Here's a good read on just about everything you need to know when it comes to commas.
What Is a Comma?
Commas are used to indicate a pause and not to end a sentence as a period does. Think about separating clauses, words, or ideas and the comma is all yours in the taking.
Comma with Subjects and Verbs
In most cases, you are not required to use a comma to separate subjects from their verbs. Here's an example:
Frank's best color, is also my favorite.
The above sentence is not a particularly great way to use the comma. The primary cause of this problem is that speakers tend to pause when reading sentences like this. In writing, however, you don't want to insert a comma as it makes the sentence slightly unnatural.
So, "Frank's best color is also my favorite" works just fine.
Comma Between Two Nouns in a Compound Subject or Object
It's wrong to say;
Duke, and his brother have been included in the team.
Duke and his brother have been included in the team.
And when serving as a compound object, it's not right to say;
My sister and her friend will visit John, and his brother later today.
My sister and her friend will visit John and his brother later today.
Comma Between Two Verbs in a Compound Predicate
Compound predicates are formed when you use a subject that is involved in more than one activity. In cases where you have two verbs in a compound predicate, you'll want to ditch the comma. So;
Tom will write, and debug the code is better expressed;
Tom will write and debug the code.
Unless there is a chance of misinterpretation, don't use a comma. Below is an example of where it would be okay to use a comma;
Mary saw her high school friend enter the room, and gestured.
Since it was Mary who gestured, inserting a comma makes it easier not to misread the statement to mean the gesture was made by her high school friend.
Using a comma when joining two independent clauses as it's not strong enough to do so. A conjunction or semicolon must be used in this situation. E.g.
"The class had already started, I stayed outside" is wrong, and the comma splice can be fixed by using a semicolon or adding a conjunction. The statement therefore becomes;
The class had already started, so I stayed outside or
The class had already started; I stayed outside.
Comma After Introductory Phrase
Participial phrases introducing a sentence are usually followed by a comma. E.g.
Angry at her brother for his mistake, Mercy left the room.
A comma can also be inserted if chances exist of misreading the sentence. So, it's right to say.
After sleeping, he left for the next class
After sleeping he left for the next class.
Comma Within a Comparison
It's wrong to use a comma when making a comparison. For example;
"He is smarter, than his friend."
"He is smarter than his friend."
Commas with Interrupters or Parenthetical Elements
When you want to add an extra bit of information in the middle of a sentence or emphasize an emotion, a comma should be used. Thus, it is wrong to say;
My best friend's cat his name is Carl is surely one of a kind.
My best friend's cat, his name is Carl, is surely one of a kind.
Hassan unlike his friend is very friendly is also better expressed as;
Hassan, unlike his friend, is very friendly.
Comma with a Question Tag
A comma should always be used before a question tag at the end of a statement. E.g.
Grammar is such an interesting topic, isn't it?
Grammar is such an interesting topic isn't it?
Comma with Direct Address
Use a comma when directly addressing someone. Thus, you say;
Peter, get the phone.
Comma with an Appositive
Appositives are words or phrases used to provide additional information about a noun. They are called "nonessential appositives" if they can be removed without altering the meaning of a sentence but called "essential appositives" if they are critical to better understanding the sentence. Nonessential appositives are set off with commas while essential ones are not.
My cousin, Andy, is a skillful footballer.
Salad, my favorite meal, is absolutely delicious.
The skillful footballer Messi just scored a beautiful goal
John's book Lightning is now a best seller.
Commas in Dates
Commas should be used to set off the year when writing a date in month-day-year format.
Judith was born on Thursday, June 1, 1995.
A comma is not needed when using the day-month-year format. Thus:
Their arrival date has been set for 1 Jan 2019.
Comma Between Coordinate Adjectives
Adjectives are coordinate when they have an equal degree of modification on a noun, and a comma should be used to separate them. So, if a sentence still sounds great after switching the order of the adjectives, they are likely to be coordinated.
For example, you can say;
His friend is a handsome, unassuming, intelligent bloke.
His friend is an unassuming, handsome, intelligent bloke.
However, a comma should not be used for adjectives that are not coordinate. Thus;
"The brilliant little kid is Mike's son" is correct, and;
"The little brilliant kid is Mike's son" is wrong.
Comma Before But
A comma should be used to join two independent clauses
Roy is a fabulous writer, but he's an even better speaker.
However, a comma should not be used if but is not joining two independent clauses
Ben is friendly, but principled should not be used
The statement is better expressed:
Ben is friendly but principled.
Comma Before And
If there are only two items on a list, using a comma to set them off is plain wrong. Thus:
Dan's cat looks adorable, and gentle is incorrect. Replace with:
Dan's cat looks adorable and gentle.
Commas with Lists
If you are making a list of more than two items, a comma should be used to separate them. However, the final comma before the and is not compulsory. Thus;
My favorite foods are rice, salad, yam, and potatoes and
My favorite foods are rice, salad, yam, and potatoes are both correct.
Comma Separating a Verb and Its Object
Commas should not be used to separate transitive verbs from their direct objects.
I'm happy I called, Peter to come over is wrong. But;
I'm happy I called Peter to come over is right.
Comma with Nonrestrictive Clause
This type of clause gives additional information on a previously mentioned thing but is not key to identifying that thing. Which and who are common ways to introduce such clauses, and a comma should be used. E.g.
Mike's Hostel, where I met Anthony, is a really big hall.
The non-restrictive clause "where I met Anthony" is termed as such since Mike's Hostel is sufficiently specific.
Comma with Restrictive Clauses
In contrast to non-restrictive clauses, restrictive clauses are needed to understand the concept previously mentioned Restrictive clauses are often introduced by who or that. A comma is not needed to set off such clauses.
The Hostel, where Roberts met Anthony, is a really big hall is wrong and should be expressed;
The Hostel where Roberts met Anthony is a really big hall
Here, you are likely not to know which hostel is being talked about until the clause "where Roberts met Anthony" is mentioned, consequently making it a restrictive clause. If it is removed, the statement becomes ambiguous, and so a comma should not be inserted.
Comma Between Correlative Conjunctions
Correlative conjunctions include neither/nor, either/or and not only/but also. These conjunctions should not be set off with commas. Thus;
Neither James nor Paul was at the Reception; is correct.
Neither James, nor Paul was at the Reception.
Comma Between Direct Quote and Attributive Tag
An attributive tag identifies who is responsible for a statement or quote. They can be used after, before or in the middle of a quote and should be separated from the quote with a comma.
"How brilliant is the James," the lecturer remarked.
But the rule changes when an attributive tag follows a quotation that ends in an exclamation point or question mark in which case a comma should not be inserted.
"Don't forget to buy me an Ice cream!" John shouted.
Comma Inside Quotation Marks
It is noteworthy that commas always go after closing the quotation marks in British English, in contrast to American English, where they should be inserted before the closing quotation marks. Be sure of your audience before adopting a style.
Comma Before Parenthesis
Used to give more information, parenthesis may be followed by a comma after its closing tag, but not before its opening or closing tag. Thus;
Having arrived late for the class (and sitting in the last row), he didn't understand the topic is correct and;
Having arrived late for the class, (and sitting in the last row), he didn't understand the topic
Having arrived late for the class, (and sitting in the last row), he didn't understand the topic is incorrect.
Comma with As Well As
A comma is usually not used to set off the phrase "as well as" unless it's a part of a non-restrictive clause.
Please revise today's notes as well as the ones given before.
Today's notes, as well as the ones given before, should be revised for your test are both correct.
Comma with Such As
Commas should be used to set off the phrase "such as," especially when the phrase introduces a non-restrictive clause. Thus,
"Omnivores, such as cows and sheep, do not eat other animals" is correct.
However, you'll have to omit the comma if the phrase introduces a restrictive clause i.e.
Animals such as cows and sheep do not eat other animals.
Comma Before Too
This is optional. You can either say;
I love football too or I, too, love football. Using a comma only adds emphasis to the statement.