What is the difference in meaning between these two sentences?
My brother, who lives in Calgary, is a student.
My brother who lives in Calgary is a student.
The speaker of the first sentence has ONE brother, the speaker of the second sentence has MORE THAN ONE brother.
In both sentences, “who lives in Calgary” is a relative clause.
In the first sentence, the relative clause serves the purpose of giving the reader extra information about the subject (my brother). This is known as a NON-DEFINING RELATIVE CLAUSE. It is simply “plugged in” the sentence as extra information. Note that non-defining relative clauses are always separated by commas. Because non-defining relative clauses are not necessary, they can always be removed without hindering the comprehensibility of the sentence. Thus, removing the clause leaves us with “My brother is a student.” From this, we can infer that the speaker has only one brother.
In the second sentence, the relative clause is a DEFINING RELATIVE CLAUSE. Defining relative clauses (surprisingly enough) serve to define the preceding subject or object of the sentence (i.e. the sentence NEEDS the clause). Thus, in this case, we can infer that the use of a defining relative clause serves to determine WHICH brother is a student. (ex: My brother who lives in Calgary is a student, and my brother who lives in Vancouver is a firefighter).
Therefore, those two little commas separating the relative clause can be very important. Remember our hapless friend who upset his girlfriend with his misuse of an apostrophe? He tried to smooth things over:
Other examples of non-defining relative clauses:
My nephew David, who was given candy, was happy
Her children, who accepted candy from the creepy stranger, were never heard from again.
My roommate’s dog, which is functionally retarded, chews electrical wires.
In all of these examples, the relative clause is not necessary
Note the differences when using defining relative clauses:
The kids who/that got candy were happy
The kids who/that accepted candy from the creepy stranger were never heard from again.
The dog which/that is functionally retarded and chews on electrical wires belongs to my roommate.
In all of these examples, the relative clause is necessary
Thankfully, it doesn’t have to be this tricky. Generally speaking, with defining relative clauses that compliment people or things, “that” is the preferred relative pronoun. Using “that” instead of “who” or “which” does a few things. It helps get rid of any potential ambiguity in spoken English:
It’s also more natural sounding. Here is the first example, rewritten so the defining relative clauses use “that” instead of “who”:
– My brother that lives in Calgary is a student
– My brother, who lives in Calgary, is a student
Using “that” in a defining relative clause isn’t any more grammatically correct than “who” or “which,” but it makes things a lot clearer.
In summation: Try to avoid mixing the two types of relative clauses up, especially if you go to a school with:
GRAMMATICALLY CONSCIOUS BULLIES