What is a Main Clause in English Grammar?

For a sentence to be complete, rather than a fragment, it must include a main clause. In English grammar, a main clause (also known as in independent clause, superordinate clause, or base clause) is a group of words made up of a subject and a predicate that together express a complete concept.

To write sentences effectively, a writer must decide which information to include in the main clause and which to relegate to dependent clauses. The basic rule of thumb is to make sure the most important information goes into the main clause, while information that ties things together by providing description and nuance gets placed in a dependent clause.

Examples and Observations

In sentence structure, the simple subject is the "who, what, or where" that comprises the main focus of the sentence. The predicate is the part of the sentence (the verb) that shows the action. For example, in the sentence, "The angry bear howled ominously," the word "bear" is the simple subject and the predicate is "howled" so the main clause of the sentence would be, "The bear howled."

In "The Concise Oxford Dictionary of Linguistics," P.H. Matthews defined a main clause as "[a] clause which bears no relation, or no relation other than coordination, to any other or larger clause." Unlike a dependent or subordinate clause, a main clause can stand alone as a sentence, while two or more main clauses can be joined with a coordinating conjunction (such as and) to create a compound sentence. In the following examples, notice the main clause does not necessarily include modifying words.

"While Fern was in school, Wilbur was shut up inside his yard."
—From Charlotte's Web by E.B. White.

Main clause:

• Wilbur was shut up

Since "Fern was in school" is modified by the word "while" which is a subordinate conjunction, "While Fern was in school" is a subordinate clause, rather than a main clause.

"Dinner always took a long time, because Antonapoulos loved food and he was very slow."
—From "The Heart Is a Lonely Hunter," by Carson McCullers

Main clause:

• Dinner took a long time

Since it's modified by the word "because," another subordinate conjunction, "because Antonapoulos loved food and he was very slow" is a subordinate clause.

"I learned to type when I was 12 years old. When I finished the class my father bought me a Royal portable typewriter."
—From "The Writing Life," by Ellen Gilchrist

Main clauses:

• I learned to type
• my father bought a typewriter

Since "when I was 12 years old" and "When I finished the class" are modified by "when," yet another subordinate conjunction, they are both subordinate clauses. "My father bought a typewriter" is the main thought in the second sentence so it's the main clause.

"Yes, he can do that until his crops fail one day and he has to borrow money from the bank."
—From "The Grapes of Wrath," by John Steinbeck

Main clauses:

• he can do that
• he has to borrow money

Since these two clauses are joined by the conjunction "and," they are both main clauses.

Sources

Matthews, P. H. "Main Clause," cited from "The Concise Oxford Dictionary of Linguistics." Oxford University Press, 1997