Rules for Using Commas
WHY USE A COMMA?
Commas serve a variety of uses, but their main purposes are to indicate a pause in the sentence or to clarify meaning for
the reader.
TERMS TO KNOW TO UNDERSTAND COMMA RULES:
Clause: A group of words that contains both a subject and a verb
Example: Patrick loves music.
Types of clauses:
● Independent clause: A clause that contains a subject and a verb and can stand alone as a sentence
○ Example: Jim studied for his chemistry quiz.
● Dependent clause: A clause that cannot stand alone as a sentence. Therefore, it depends on being linked with
an independent clause to form a complete sentence.
○ Example: Jim studied for his chemistry quiz after he finished his English Composition essay.
● Essential clause: In a sentence with an ambiguous/general noun, an essential clause limits this noun and tells us
“which one?”
○ Example: The woman who interviewed you is my sister.
● Nonessential clause: A clause that describes a noun, but is not necessary to define an ambiguous noun
○ Example: My uncle, who is eighty years old, walks three miles every day.
Coordinating conjunction: A word used to combine two independent clauses. You can remember the independent
clauses with the acronym FANBOYS: For, And, Nor, But, Or, Yet, So
Example: Sarah is an undergraduate student, but she is already conducting independent research.
HOW TO USE COMMAS:
Dependent Clause: Do not put a comma after the main clause when it is followed by a dependent clause.
● Example with mistake: I walked to campus, while listening to music.
● Correction: I walked to campus while listening to music. [“I walked to campus” is the main clause. “While
listening to music” is the dependent clause. You do not need a comma separating them.]
Compound sentences: A compound sentence contains two independent clauses joined by a coordinating conjunction.
The comma is placed before the coordinating conjunction.
● Example with mistake: I like going to school but I don’t like doing homework.
● Correction: I like going to school, but I don’t like doing homework. [“I like going to school” and “I don’t like doing
homework” are both independent clauses. They are joined by the coordinating conjunction “but.” The comma is
necessary before “but.”]
● Note that logical connectors (meanwhile, however, nevertheless) cannot be used as coordinate conjunctions
and are used instead at the beginning of a sentence.
Nonessential clauses vs. essential clauses: Do not separate essential clauses from the rest of the sentence with
commas. Note that essential clauses often begin with “that.” Nonessential clauses should be separated with commas.
● Example: The book that I borrowed from you is excellent. [“That I borrowed from you” is an essential clause.
Therefore, no commas are needed.]
● Example: Apples, which are my favorite fruit, are the main ingredient in this recipe. [“Which are my favorite
fruit” is a nonessential clause, so it is set apart from the rest of the sentence with commas.]
Lists: Use commas to separate three or more words, phrases, or clauses written in a series. You can, but do not need to,
include the final comma if there is a conjunction.
● Example: I like to enjoy my evenings by relaxing, reading, and cooking in my kitchen. [This example uses the
final comma.]
● Example: I like to enjoy my evenings by relaxing, reading and cooking in my kitchen. [This example does not use
the final comma, but it is still correct.]
Quotations: Use commas to shift between the identifying clause and a quotation.
● Example: Mary said, “I’m going to the movies later.”
● Example: “I’m going to the movies later,” said Mary.
● Example: “I’m going,” said Mary, “to the movies later.”
Introductory clauses/phrases/words: A sentence often requires a word, phrase, or clause before the main idea in order
to indicate cause and effect, time, contrast, or a transition of some kind. This is often a dependent clause. There is a
comma separating the introductory clause/phrase/word from the main clause of the sentence.
● Example: Because I wanted to arrive to the concert on time, I left my house early. [“Because I wanted to arrive
to the concert on time” is the introductory clause, so it is followed by a comma.]
● Example: Although I arrived on time, the Professor marked me tardy. [“Although I arrived on time” is the
introductory clause, so it is followed by a comma.]
● Example: However, you may not be satisfied with the results. [“However” is the introductory word, so it is
followed by a comma.]
End of sentence: Use a comma near the end of a sentence to separate contrasted coordinate elements or to indicate a
distinct pause or shift.
● Example: The birds seemed menacing, almost evil.
● Example: He was vertically challenged, not short.
COMMON COMMA MISTAKES
Comma splicing: Do not join two independent clauses without a coordinating conjunction.
● Example with mistake: Patrick loves music, he plays in a band.
● Correction: Patrick loves music, so he plays in a band. [“Patrick loves music” and “he plays in a band” are both
independent clauses, so they need to be joined with both a comma and a coordinating conjunction. Here, the
coordinating conjunction is “so.”]
Dependent clause following an Independent clause: Do not put a comma after the main clause when a dependent
clause follows it.
● Example with mistake: She went to the store, because she wanted to buy cookies.
● Correction: She went to the store because she wanted to buy cookies. [“She went to the store” is an
independent clause, and “because she wanted to buy cookies” is a dependent clause. Do not use a comma to
separate these clauses.]
