Comma usage is definitely a big problem for all learners of English. Although, comma usage has nothing to do with your English abilities (here I am talking about speaking and listening skills because this is what every English learner cares about), it is of a real help when it comes to writing. Most of the English learners (at least here in Vietnam) use English at work for communication purposes, especially written English (in form of emails, reports etc) with their business partners or foreign managers.
Comma usage rules
Use comma in enumerations – here you can consider the words separated by comma as a list of items. There must be at least three words in the list.
I saw a zebra, a crocodile, a snake, and a giraffe.
Use comma in enumerations before “and” – Using comma before “and” in an enumeration is a usual practice but it is optional. Don’t use comma before “and” if a group of two or more words form a unit – There is a situation in which using comma before “and” is wrong. In the example below “eggs and cheese” represents a dish (a unit) and comma usage is not required.
Today we serve pizza, spaghetti, eggs and cheese, hamburger, and noodle soup.
Use comma in compound numbers – Unlike other languages (for example Romanian and Vietnamese ) comma is used in compound numbers (Romanian and Vietnamese use period in this situation).
Romanian and Vietnamese: $10.455.012
Comma is not used in decimals – Use period to separate numbers and decimals.
Romanian and Vietnamese: $5,95
Use comma in dates – Many times a date is given in the following format: month/ day/ year. In this situation we have to use comma before the year in the date. However, if only the month and the year is given, then you shouldn’t use comma before the year.
June 16th, 1977
Use comma after a name if you address directly to someone – If there is a group of people and you address to a particularly person, then usage of comma is required.
John, can you come here for a moment?
Use comma after salutations – Letters and emails require a salutation at the very beginning (e.g. Dear Sir, Dear Mr. Smith etc). A comma after salutations is always required in this situation. However, according to some grammarians, comma shouldn’t be use after salutations in business letters. In business letters don’t use comma (British English) or use a colon (American English).
Dear Mr. Smith, (in private letters and emails)
Dear Mr. Smith (business letters – British English)
Dear Mr. Smith: (business letters – American English)
Use comma after greetings at the end of the letters or emails – Every letter or email finishes with something like “Sincerely” or “Best regards”. Comma in this situation is optional.
Use comma for separating parts of an address – Parts of an address are always separated by comma.
My address is 180 CMT Street, District 3, Ho Chi Minh city, Vietnam.
Use comma after coordinating conjunctions – Coordinating conjunctions (and, but, for, or, nor, so, yet) that separates two independent clauses have to follow a comma.
Today is my day off, so in the evening I am visiting my friend.
Don’t use comma between a main clause and a subordinate clause – Here we have two situations.
If the main clause is followed by the subordinate clause – comma is not required between the main clause and the subordinate clause.
My friend called me while I was eating.
If the main clause follows the subordinate clause – comma is required between the main clause and the subordinate clause.
While I was eating, my friend called me.
Use comma after introductory phrases – These introductory phrases can be: nonessential appositive phrases, absolute phrases, long prepositional phrases, infinitive phrases and participle phrases.
Note: Long prepositional phrases are those phrases that consist of at least five words.
Having finished the article about comma usage, I turned off my computer.
Use comma after “yes”, “well” and “however” if these words are placed at the beginning of the sentence – Yes, well, and however are considered introductory words, so comma usage is required.
Yes, you should cancel your trip.
Use comma before and after a phrase, clause or single word that is not essential to the meaning of the sentence – Of course, that phrase, clause, or single word has to be placed in the middle of the sentence.
That Monday, which is a legal holiday, I was asked to go to work.
Comma usage in relative clauses – Here we have two situations. Don’t use comma to separate essential elements. Use comma to separate non essential elements.
Dan, who is from Romania, is an English Teacher in Vietnam.
The man who is from Romania is an English Teacher.
Use comma before “please” – If “please” is placed at the beginning of the sentence, then there is no comma requirement. If “please” is placed at the end of the sentence, then comma has to be used before “please”.
Please come and help me.
Come and help me, please.
Use comma with “if” clauses – We have two situations here. “If” clause at the beginning of the sentence require to be followed by a comma. “If” clause at the end of the sentence doesn’t require comma usage.
If I go to Romania, I will eat a lot of cheese.
I will eat a lot of cheese if I go to Romania.
Use comma with opposites – There are some situations when two opposites are used in the sentence and they are separated by “and” or “but”. Comma is required in this situation.
It was a teacher, and not a student, who broke the window.
Use comma for enhancing readability – In some situations comma is required, otherwise the readers might be confuse.
Above, the sky was blue ...
Above the sky was blue ...
Use comma before question tags – Question tag means that a declarative statement is turned into a question.
I have told you, haven’t I?
Use comma in direct speech – Here we have three situations. Direct speech is at the beginning of the sentence – a comma before the ending quotation mark is required. Direct speech is at the end of the sentence – comma before the first quotation mark is required. Direct speech finishes with question mark or exclamation mark – comma usage is not required.
“I should kill you”, she said.
She said, “I should kill you”.
“Should I kill you?” she asked.
Use comma after adverbs – The following adverbs have to be followed by a comma: in fact, therefore, however, nevertheless, too, instead, and still. These adverbs follow and precede a comma if they are in the middle of a sentence.
In fact, he even doesn’t speak French.
The car, however, looks very good.
Use comma between two adjectives – Comma has to be used if the adjectives give information of the same importance. To find out if two adjectives give information of the same importance, place an “and” between them. If the sentence sounds right with the “and” between adjectives, then the adjectives give information equally important.
She has long, black hair.
She has long and black hair.