Relative Clauses

Understanding Relative Clauses

Relative clauses are dependent clauses that provide additional information about a noun in a sentence. They make your writing more sophisticated and help you avoid repetition by combining related ideas into one sentence.

Two Main Types of Relative Clauses

1. Defining Relative Clauses

Defining relative clauses (also called restrictive clauses) provide essential information that identifies which person or thing you're talking about. Without this clause, the meaning becomes unclear.

Structure: noun + relative pronoun + verb + ...

Examples:
- The researcher who discovered the vaccine won the Nobel Prize.
- The conference that I attended last month was in Barcelona.
- The data which shows positive results supports our hypothesis.

Notice: No commas are used in defining relative clauses.

2. Non-defining Relative Clauses

Non-defining relative clauses (restrictive clauses) provide extra information about a noun that is already identified. This additional detail could be removed without changing the core meaning.

Structure: noun + , + relative pronoun + verb + , + ...

Examples:
- Dr. Elena Martinez, who is a leading expert in neurology, has published over 200 papers.
- The Amazon rainforest, which covers 5.5 million square kilometers, is home to 10% of Earth's species.
- My colleague James, whom I've worked with for five years, is moving to Singapore.

Notice: Non-defining clauses are separated by commas.

Relative Pronouns and Their Uses

Important Grammar Rules

When to Use "that" vs. "which"

• Use that in defining clauses: "The laptop that has the broken screen needs repair."
• Use which in non-defining clauses: "My laptop, which I bought last year, needs repair."
• In American English, "that" is preferred in defining clauses; "which" for non-defining clauses.

Subject and Object Relative Pronouns

Subject pronouns (the relative pronoun performs the action):
- "The engineer who designed the bridge received recognition."

Object pronouns (the relative pronoun receives the action):
- "The engineer whom we hired designed the bridge." (Alternative: "The engineer that we hired...")

Common Mistakes to Avoid

1. Mixing clause types with commas
   - ❌ "The research, that I conducted, shows interesting results."
   - ✓ "The research that I conducted shows interesting results." (defining, no commas)
   - ✓ "My research, which took three years, shows interesting results." (non-defining, commas)

2. Using "which" for people
   - ❌ "The student which won the prize is talented."
   - ✓ "The student who won the prize is talented."

3. Omitting necessary relative pronouns
   - ❌ "The experiment we conducted proved the theory." (acceptable in informal speech)
   - ✓ "The experiment that we conducted proved the theory." (clearer)

4. Unnecessary repetition of the antecedent
   - ❌ "The employee who he works here is excellent."
   - ✓ "The employee who works here is excellent."

Practice Tips

• Read widely to see relative clauses in context. Notice how professional writers use them.
• Convert two sentences into one using relative clauses: "Sarah is a biochemist. She specializes in protein research." → "Sarah, who is a biochemist, specializes in protein research."
• Identify the antecedent first before deciding which relative pronoun to use.
• Check for commas to determine if a clause is defining (no commas) or non-defining (with commas).
• Practice with your own examples from your field of study or interest.