Humanities › English Subordination With Adjective Clauses Sentence Structures in English Grammar Share Flipboard Email Print In the following sentence, the word group in italics is an adjective clause: "My father, who is a superstitious man, always sets his unicorn traps at night.". Tim Graham/Getty Images English English Grammar An Introduction to Punctuation Writing By Richard Nordquist English and Rhetoric Professor Ph.D., Rhetoric and English, University of Georgia M.A., Modern English and American Literature, University of Leicester B.A., English, State University of New York Dr. Richard Nordquist is professor emeritus of rhetoric and English at Georgia Southern University and the author of several university-level grammar and composition textbooks. our editorial process Richard Nordquist Updated July 25, 2018 In English grammar, coordination is a useful way of connecting ideas that are roughly equal in importance. But often we need to show that one idea in a sentence is more important than another. On these occasions, we use subordination to indicate that one part of a sentence is secondary (or subordinate) to another part. One common form of subordination is the adjective clause (also called a relative clause)--a word group that modifies a noun. Let's look at ways to create and punctuate adjective clauses. Creating Adjective Clauses Consider how the following two sentences might be combined: My father is a superstitious man.He always sets his unicorn traps at night. One option is to coordinate the two sentences: My father is a superstitious man, and he always sets his unicorn traps at night. When sentences are coordinated in this way, each main clause is given equal emphasis. But what if we want to place greater emphasis on one statement than on another? We then have the option of reducing the less important statement to an adjective clause. For example, to emphasize that father sets his unicorn traps at night, we can turn the first main clause into an adjective clause: My father, who is a superstitious man, always sets his unicorn traps at night. As shown here, the adjective clause does the job of an adjective and follows the noun that it modifies--father. Like a main clause, an adjective clause contains a subject (in this case, who) and a verb (is). But unlike a main clause an adjective clause can't stand alone: it has to follow a noun in a main clause. For this reason, an adjective clause is considered to be subordinate to the main clause. For practice in creating adjective clauses, try some exercises in Sentence Building With Adjective Clauses. Identifying Adjective Clauses The most common adjective clauses begin with one of these relative pronouns: who, which, and that. All three pronouns refer to a noun, but who refers only to people and which refers only to things. That may refer to either people or things. The following sentences show how these pronouns are used to begin adjective clauses: Mr. Clean, who hates rock music, smashed my electric guitar.Mr. Clean smashed my electric guitar, which had been a gift from Vera.Mr. Clean smashed the electric guitar that Vera had given me. In the first sentence, the relative pronoun who refers to Mr. Clean, the subject of the main clause. In the second and third sentences, the relative pronouns which and that refer to guitar, the object of the main clause. Punctuating Adjective Clauses These three guidelines will help you decide when to set off an adjective clause with commas: Adjective clauses beginning with that are never set off from the main clause with commas. Food that has turned green in the refrigerator should be thrown away.Adjective clauses beginning with who or which should not be set off with commas if omitting the clause would change the basic meaning of the sentence. Students who turn green should be sent to the infirmary. Because we don't mean that all students should be sent to the infirmary, the adjective clause is essential to the meaning of the sentence. For this reason, we don't set off the adjective clause with commas.Adjective clauses beginning with who or which should be set off with commas if omitting the clause would not change the basic meaning of the sentence. Last week's pudding, which has turned green in the refrigerator, should be thrown away. Here the which clause provides added, but not essential, information, and so we set it off from the rest of the sentence with commas. Now, if you're ready for a short punctuation exercise, see Practice in Punctuating Adjective Clauses.