Commas or No commas? (In Relative Clauses)

Let’s break this down clearly. Relative clauses—those bits of a sentence that give extra info about a noun—come in two flavours: defining (also called restrictive) and non-defining (non-restrictive). Commas depend on which type you’re dealing with and how the clause fits into the sentence. Here’s the rundown:

Defining Relative Clauses (No Commas)

• What they do: They pinpoint (or DEFINE) exactly which person, thing, or idea you’re talking about. Without them, the sentence would be vague or incomplete.
• Comma rule: No commas. The clause is essential, so it flows right into the sentence.
• Pronouns: Usually that, who, whom, or which (though that is common in informal English).
• Examples:
  • “The book that I borrowed is on the table.”
    (No commas—tells you which book.)
  • “People who live here are friendly.”
    (No commas—specifies which people.)
  • “The car which she drives is red.”
    (No commas—defines which car.)

If you add commas here, it changes the meaning or sounds wrong. For instance, “The book, that I borrowed, is on the table” is incorrect because that doesn’t work with commas, and the clause is defining.

Non-Defining Relative Clauses (With Commas)

• What they do: They add extra, non-essential info. The sentence still makes sense without them—like a bonus detail.
• Comma rule: Use commas to set them off. Think of the commas as parentheses: the clause is detachable.
• Pronouns: Usually who, whom, or which (never that).
• Examples:
  • “My sister, who lives in Paris, is visiting tomorrow.”
    (Commas—extra info about a specific sister; the sentence works without it: “My sister is visiting tomorrow.”)
  • “This phone, which I bought last week, has a great camera.”
    (Commas—adds a detail, but “This phone has a great camera” stands alone.)
  • “Mr. Jones, whom I met yesterday, is our new boss.”
    (Commas—extra info about a known Mr. Jones.)

Without commas, it becomes defining and shifts the meaning. “My sister who lives in Paris is visiting” implies I have multiple sisters, and only the Paris one is coming.

Key Differences in Action

• Defining (no commas): “The man who robbed the bank was caught.”
  (Which man? The one who robbed the bank—essential.)
• Non-defining (with commas): “The man, who was tired, sat down.”
  (We know who the man is; the tiredness is just extra.)

Tricky Bits

1. Proper Nouns: Non-defining clauses often follow names (e.g., “Sarah, who loves coffee, smiled.”) because the name already identifies the person—no defining needed.
2. That vs. Which: That is more commonly used for defining (no commas), but which can be used as well (particularly in British English): “The movie that I watched was great.” or “”The movie which I watched was great.” Which with commas is non-defining: “The movie, which I watched, was great.” That, on the other hand, cannot be used for non-defining sentences like this.
3. Dropping the Pronoun: In defining clauses, you can skip the pronoun if it acts as the object of the clause (not the subject) (“The book I borrowed is great”), but never in non-defining ones.

Expanded Examples of when to drop and when to not drop the pronoun:

• Defining (Can Drop the Pronoun if Object):
  • With pronoun: “The book that I read is fascinating.”
    (Subject: “I”; object: “book” → that can be dropped.)
• • Without pronoun: “The book I read is fascinating.”
    (Still clear, informal, correct.)
• • With pronoun: “The person whom she met is kind.”
    (Subject: “she”; object: “person” → whom can be dropped.)
• • Without pronoun: “The person she met is kind.”
    (Correct, informal.)
  But if the pronoun is the subject, you can’t drop it:
  • “The dog that chased the cat is mine.”
    (Subject: “that” → can’t drop that: “The dog chased the cat is mine” is wrong.)
• Non-Defining (Cannot Drop the Pronoun):
  • With pronoun: “My dog, who loves to run, is playful.”
    (Subject: “who”; object: “dog” → who is required; dropping it is incorrect: “My dog, loves to run, is playful” is wrong.)
  • With pronoun: “This car, which I bought, is fast.”
    (Subject: “which”; object: “car” → which is required; dropping it is incorrect: “This car, I bought, is fast” is wrong.)

4. Multiple Relative Clauses in One Sentence: You can have both defining and non-defining clauses in the same sentence, but you need to use commas and pronouns correctly to avoid confusion.

Examples:

• “The book that I borrowed, which was written by a famous author, is on the shelf.”
  (“That I borrowed” is defining, no commas, that—essential to identify the book. “Which was written…” is non-defining, with commas, which—extra info about the known book.)
• “My friend John, who lives in London, who I met at university, is visiting.”
  (Both are non-defining, with commas, who—extra details about a specific John.)

5. Ambiguous Nouns: Sometimes, a noun’s uniqueness isn’t clear, making it hard to decide if the clause is defining or non-defining.

Examples:

• “The teacher who teaches math is strict.”
  (Defining, no commas—implies multiple teachers, specifying which one.)
• “The teacher, who teaches math, is strict.”
  (Non-defining, with commas—implies one teacher, and math teaching is extra info.)

Quick Recap

• If the clause answers “which one?” and you can’t remove it without confusion, it’s defining—no commas.
• If it’s just extra info and the sentence still stands alone, it’s non-defining—use commas.

So, commas are your clue: no commas = must-have info; commas = nice-to-know info.

Quiz