Understanding Relative Clauses: Defining and Non-Defining

In English grammar, relative clauses are an essential tool for adding detail and clarity to sentences. They help us connect ideas, provide more information about a noun, and create complex, nuanced expressions. Among these, the two main types are defining relative clauses and non-defining relative clauses. Understanding their structure and usage can significantly enhance your writing and speaking skills.

This blog delves into relative clauses, breaking down their components, functions, and differences to give you a clear understanding.

What Are Relative Clauses?

A relative clause is a type of subordinate clause that modifies a noun or pronoun in a sentence. These clauses begin with a relative pronoun, such as who, whom, whose, which, or that, or sometimes a relative adverb like when, where, or why.

For example:

• The book that I borrowed was fascinating.
  (The relative clause “that I borrowed” modifies “the book.”)

Relative clauses provide extra information about the noun, and depending on their type, this additional detail may be essential or non-essential to the sentence’s meaning.

Defining Relative Clauses

A defining relative clause, also known as a restrictive clause, provides information that is essential to identifying the noun it modifies. Without this clause, the meaning of the sentence would be incomplete or unclear.

Key Characteristics of Defining Relative Clauses:

1. Essential Information: The clause specifies which person, thing, or place you are talking about.
   Example:
   • The man who fixed my car is very skilled.
     (Without “who fixed my car,” we wouldn’t know which man is being referred to.)
2. No Commas: Defining relative clauses are not set off by commas because the information is crucial to the sentence.
   Example:
   • The house that she bought is near the beach.
     (No commas are used because the clause “that she bought” is essential to understanding which house is being discussed.)
3. Relative Pronouns Can Be Omitted in Certain Cases: When the relative pronoun functions as the object of the clause, it can often be omitted in informal English.
   Example:
   • The dress (that) she wore was beautiful.
     (The relative pronoun “that” is optional here.)

Examples of Defining Relative Clauses:

• People who live in glass houses shouldn’t throw stones.
• The car that I rented broke down on the highway.
• This is the book which won the award last year.

Non-Defining Relative Clauses

A non-defining relative clause, also known as a non-restrictive clause, provides additional information that is not essential to the sentence’s core meaning. The sentence would still make sense if the clause were removed.

Key Characteristics of Non-Defining Relative Clauses:

1. Extra Information: The clause offers supplementary details about the noun or pronoun, which are not needed to identify it.
   Example:
   • My sister, who lives in Paris, is visiting us next week.
     (The clause “who lives in Paris” provides extra information but is not necessary to identify “my sister.”)
2. Commas Are Used: Non-defining relative clauses are always separated from the rest of the sentence by commas.
   Example:
   • The Eiffel Tower, which is located in Paris, is a famous landmark.
     (The commas indicate that the clause is additional information.)
3. Relative Pronouns Cannot Be Omitted: In non-defining clauses, the relative pronoun must always be present.
   Example:
   • The painting, which was created in 1905, is worth millions.
     (You cannot omit “which” in this sentence.)
4. No Use of “That”: In non-defining clauses, you cannot use “that” as the relative pronoun.
   Example:
   • Incorrect: The river, that flows through the city, is polluted.
   • Correct: The river, which flows through the city, is polluted.

Examples of Non-Defining Relative Clauses:

• My neighbor, who is a doctor, helped me last night.
• The museum, which was recently renovated, attracts thousands of visitors every year.
• Mr. Johnson, whose son is my classmate, is a kind man.

Comparing Defining and Non-Defining Relative Clauses

Relative Pronouns and Their Functions

Relative clauses depend heavily on relative pronouns. Here’s a quick overview of their usage:

Common Mistakes and Tips

1. Misusing Commas:
   • Incorrect: The dog, that barks a lot, is my neighbor’s.
   • Correct: The dog that barks a lot is my neighbor’s.
     (No commas are needed for defining clauses.)
2. Overusing “That”:
   • Incorrect: The Eiffel Tower, that is in Paris, is famous.
   • Correct: The Eiffel Tower, which is in Paris, is famous.
     (Use “which” for non-defining clauses.)
3. Omitting Relative Pronouns in Non-Defining Clauses:
   • Incorrect: My friend, I met yesterday, is kind.
   • Correct: My friend, whom I met yesterday, is kind.
4. Choosing the Wrong Pronoun:
   • Incorrect: The man which helped me is here.
   • Correct: The man who helped me is here.
5. Avoid Overcomplicating Sentences: Relative clauses are powerful, but overusing them can make sentences convoluted. Break complex ideas into shorter sentences if necessary.

How to Use Relative Clauses Effectively

1. Enhance Description:
   Use relative clauses to enrich your sentences with detail. For instance:
   • The house, which has a garden, is on sale.
   • The house that has a garden is on sale.
2. Create Variation:
   Mix defining and non-defining clauses to add rhythm to your writing.
3. Tailor Your Tone:
   Non-defining clauses often have a formal tone, while defining clauses are more direct and practical.
4. Practice:
   Experiment with sentences, varying the placement and type of relative clauses.

Conclusion

Relative clauses are a cornerstone of effective communication in English. Defining relative clauses are essential for identifying specific nouns, while non-defining relative clauses add extra, non-essential detail. Understanding their differences and mastering their usage can make your writing more descriptive, precise, and engaging.

By practicing these distinctions and incorporating them thoughtfully, you can enhance your ability to craft clear and impactful sentences, whether in formal writing or everyday conversation.