Comma, primarily, functions in three ways, by introducing, by separating and by enclosing. Comma indicates a mild pause, hence, is subtle, elusive nature. A comma can work in following way:


          Ravi said, “It’s is very nice movie.”          

Comma is not used with a quoted reference which is subject or object of a sentence.   

•    The president spoke on “Our relations with Latin America.”  
•    Obey the “slow down” signs.

Comma is not used before a quotation starting with conjunction that.     

•    The travel poster suggested that “California is the land of sunshine.”

•    “It is a grand day,” Bill said. (Position of Comma)

Comma is not used in addition to a question mark or mark of exclamation following a quotation.

            “Do you think we can leave early?” he asked.    


Commas are used to separate words, phrases, and clauses in a series.

•    Our American professors like their literature clear, cold, pure, and very dead.      

A comma is used to separate he main (independent) clauses of a sentence joined by co-ordinating conjunctions like and, but, or, nor, for, and yet.

•    Rakesh is the best friend of mine, but he is not sure of it.             
•    It’s better to give than to lend, and it costs about the same.

      Comma is not used to separate main clauses when the clauses already contain commas within them.

Comma is not used to separate main clauses when the second clause has the same subject as the first clause and the subject is not repeated.    

•    She was a brunette by birth but a blonde by habit.

Comma is used to separate an introductory subordinate phrase or clause from a main clause. Such clauses often begin with subordinate conjunctions (when, if, because, since, while, as, although, before, after, etc.)         

•    Where all think alike, no one thinks very much. 

Comma is not used when a subordinate phrase or clause follows a main clause unless the subordinate clause expresses a non limiting idea.    

•    You must do this because I said you must.

A comma is used to separate an introductory phrase containing a participle or an infinitive used as an adjective or an adverb.

•    Drawing on my fine command of knowledge, I said noting.   

A comma is not used to separate a gerund or an infinitive phrase that is the subject in the sentence.

•    Writing carelessly causes bad grades.   

Commas are used to enclose non-limiting (also called “non-restrictive”) phrase and clauses within the sentence. Though it may add information and help clarify meaning, a non-limiting phrase or clause is not necessary to identify the word or words it modifies. It can be omitted from the sentence without changing the meaning. A limiting (also called “restrictive”) phrase or clause, however, is necessary to identify the word or words it modifies. An integral part of the sentence, a limiting phrase or clause is not enclosed in commas.

•    Non-limiting: The spirit of St. Louis, which Lindenbergh flew across the Atlantic, was a single-engine airplane.   
•    Limiting: The airplane that Lindenberg flew across the Atlantic was The spirit of St.Louis.