Adjective Clauses & Phrases

An adjective clause is a group of words that contains a subject and a verb and describes a noun, just like an adjective does. An adjective phrase is a shorter group of words (without a subject-verb pair) that also modifies a noun. At P6, you will master the difference between defining and non-defining adjective clauses, learn the punctuation rules that go with each type, and practise combining sentences using adjective clauses.

What You'll Learn

• How to distinguish between defining (restrictive) and non-defining (non-restrictive) adjective clauses
• How to punctuate defining and non-defining adjective clauses correctly using commas
• How to combine two sentences into one using an adjective clause
• How to recognise and use adjective phrases as shorter alternatives to adjective clauses

When to Use

1. Identifying which person or thing you mean (defining clause): "The students who revised thoroughly scored well in the PSLE."
2. Adding extra information about a specific person or thing (non-defining clause): "Marina Bay Sands, which was completed in 2010, is one of Singapore's most famous landmarks."
3. Combining two related sentences into one: "The author has won many awards. She wrote this novel." becomes "The author who wrote this novel has won many awards."
4. Using a phrase instead of a full clause for conciseness: "The man standing at the bus stop is my uncle." (adjective phrase, shorter than "The man who is standing at the bus stop...")
5. Giving background details in formal or academic writing: "The Merlion, which symbolises Singapore's origins as a fishing village, attracts millions of tourists each year."

How to Form

Defining vs Non-Defining Adjective Clauses

How to Form an Adjective Clause from Two Sentences

1. Find the shared noun that appears in both sentences.
2. Decide which sentence gives additional detail -- this becomes the adjective clause.
3. Replace the repeated noun (or pronoun) in the second sentence with the appropriate relative pronoun (who, whom, whose, which, that).
4. Place the adjective clause immediately after the noun it describes.
5. Add commas if the clause is non-defining.

Defining clause example:

• Sentence 1: The girl won the Science Olympiad.
• Sentence 2: The girl sits beside me.
• Combined: The girl who sits beside me won the Science Olympiad.

Non-defining clause example:

• Sentence 1: The Singapore Botanic Gardens were named a UNESCO World Heritage Site.
• Sentence 2: The Singapore Botanic Gardens were established in 1859.
• Combined: The Singapore Botanic Gardens, which were established in 1859, were named a UNESCO World Heritage Site.

Adjective Phrases vs Adjective Clauses

An adjective phrase does the same job as an adjective clause but is shorter because it does not contain a subject-verb pair. You can often shorten an adjective clause into an adjective phrase by removing the relative pronoun and the auxiliary verb.

Key Rules

1. Defining clauses have no commas: If the clause is needed to identify the noun, do not surround it with commas. "The children who behaved well received a reward." (Which children? The ones who behaved well.)

2. Non-defining clauses must have commas: If the clause adds extra, non-essential information, place a comma before and after it. "Mrs Lim, who has taught for twenty years, is retiring this December."

3. Do not use "that" in non-defining clauses: Always use who for people or which for things in non-defining clauses. "The durian, which is known for its strong smell, is popular in Southeast Asia." -- never "The durian, that is known for its strong smell..."

4. Proper nouns usually take non-defining clauses: Since a proper noun already identifies a specific person, place, or thing, any adjective clause that follows it is almost always non-defining. "Sentosa, which is a resort island, offers many attractions."

5. An adjective phrase must stay next to the noun it modifies: Moving the phrase away from its noun creates confusion. "Covered in mud, the dog ran into the house" is clear. "The dog ran into the house covered in mud" could mean the house is covered in mud.

6. You can shorten a clause to a phrase only when the relative pronoun is the subject: If the relative pronoun is the object of the clause, you cannot simply remove it. "The cake that my mother baked was delicious" cannot become "The cake my mother baked was delicious" as a phrase -- it remains a clause with the relative pronoun omitted.

Common Mistakes

Clue Words

Signals for a defining adjective clause (no commas):

the + common noun + who/which/that (the student who, the book that, the place which)

Signals for a non-defining adjective clause (commas needed):

proper nouns (Singapore, Mrs Tan, the Merlion) or nouns already clearly identified (my mother, our school, this building) followed by who or which

Signals that you can shorten to an adjective phrase:

who is, who are, which is, which was, which were -- remove these to create a present participle (-ing) or past participle (-ed) phrase

Tip: If you can remove the clause and the sentence still makes complete sense with a clear subject, the clause is non-defining -- add commas. If removing it makes you ask "Which one?", it is defining -- no commas needed.

Practice Tips

1. The removal test: Cover the adjective clause with your hand. Does the sentence still make sense and clearly identify the noun? If yes, the clause is non-defining and needs commas. If the sentence becomes vague or meaningless, the clause is defining and takes no commas.

2. Proper noun check: Whenever you see a proper noun (a name of a person, place, or thing) followed by an adjective clause, add commas immediately. Proper nouns are already specific, so the clause is almost always non-defining.

3. Clause-to-phrase conversion drill: Take any adjective clause containing "who is", "which is", or "which was" and try removing those words. Check whether the resulting phrase still sounds natural and sits next to the correct noun.

4. Sentence-combining practice: Pick two related sentences from your reading material and combine them using an adjective clause. Then decide: is the clause defining or non-defining? Add or remove commas accordingly.

Quick Reference