In Longman English Grammar Practice, there is a practice question in which you would say what the sentences mean with and without commas.

My brother who is in Canada is an architect.

Without commas: I have another brother or other brothers somewhere else.

With commas: I have only one brother.

I am perplexed by this. How do you come to this answer? I thought the whole use of commas in this instance was to provide additional, unnecessary information. If there are commas used, then it means that him living in Canada is just additional information that has no relation to him being an architect. If commas are not used, then him living in Canada is important for him being an architect. Please correct me if I am wrong.

3 Answers 3


This part of your understanding is correct: if commas were used in your examples, it would provide additional information. However, the rest of your understanding is not quite correct.

The subtle (but important) difference is about implications.

Let's try a simple example (not a relative clause):

John: Hi, Jane! I've heard that you start learning Japanese calligraphy. Have you already bought a brush?
Jane: a) Yes, I have. I bought one.
Jane: b) Yes, I have. I have one with me. Would you like to see it?

Both the answers in a) and b) say one, but with different implications. In a), it's implied that Jane has only one brush. In b), it's very likely that Jane has more than one brushes, and she happens to have one with her at the time.

Your example is similar. Let's make it more obvious.

with commas: My brother, who is in Canada, is an architect.
without commas: My brother who is in Canada is an architect.

With commas (technically, this is called a non-restrictive relative clause), you can simply read it as "My brother is an architect." This implies that you have only one brother. It's not necessarily so, but it's very likely so (because you could've phrased it another way otherwise, e.g. One of my brothers is an architect). So, if your context doesn't suggest otherwise, the reader may and probably will assume that you have only one brother if you write it that way.

Without commas (this is called a restrictive relative clause), it will be somewhat like Jane's alternative b) (I have one with me). It implies that you have more than one brother. Besides your brother who is now in Canada, you still have more brother or brothers, probably somewhere else.

This, again, will depend on your context. It's not necessarily so. But without any further clarification, your reader may and probably will assume so. Thus, it's a fair point that a grammar book would make, because we would want to write as clear as possible and avoid any possible misleading in our writing.

As for this assumption, "If commas are not used, then him living in Canada is important for him being an architect," it may or may not be so. Your context may suggest so. But without any specific context, My brother who is in Canada is an architect, simply means that you're talking about your brother or one of your brothers, who is in Canada, who is an architect.


The clause "who is in Canada" and the predicate "is an architect" are not directly related.  With or without commas, being in Canada is not essential to our understanding of the word "architect".

If "who is in Canada" is essential, then it is essential to the phrase in which it occurs.  It would be essential to our understanding of the word "brother".

Consider this sentence first:

My brother is an architect.

You can think of "my" as essential to the phrase "my brother".  It lets us know which one brother this particular brother is.  There are billions of brothers in the world.  If I have only one brother, then the phrase "my brother" identifies exactly one human being.

If I have more than one brother, then I need to say more than "my brother" to indicate which one specific person I mean.  I could talk about my older brother or my younger brother.  The words "older" and "younger" are then essential to make the word "brother" mean one specific human being.  Alternately, I might be able to talk about my Canadian brother and my Mexican brother.

When "who is in Canada" is essential, it implies that I have only one brother in Canada and at least one brother somewhere else.  Otherwise, I wouldn't need it in order to indicate just this one brother.

I have one brother who lives in Canada.  He is an architect. 
My brother who lives in Canada is an architect. 

Let's go back to the idea that I have only one brother.  If so, it's only essential that I say "my brother" to indicate one person.  That he is in Canada is incidental.  It's extra information about my brother. 

I have one brother.  He is an architect.  He also happens to be in Canada. 
My brother, who is in Canada, is an architect. 

When commas are used, it means that his living in Canada is just additional information that we don't need to identify this particular person.  When commas are not used, it means that we need the fact that he is in Canada to identify which person this brother is. 

In either case, being in Canada and being an architect are unrelated, except that both things are things about my brother.


I think it's best (though others disagree) to approach punctuation as a set of minimalist notations that attempt to reflect a very limited range of speech behaviors.

In speech, the syntactic boundaries of a phrase or a clause are marked by pauses of differing duration (usually lasting only fractions of a second) and also by intonational contours. Even a microsecond pause or a subtle shift in tonality can resolve ambiguities in conversation.

Writing conventions approximate these natural expressive cues with punctuation. Punctuation reflects the internal structure of the sentence, identifying the role played by phrases and clauses. Some marks like the question mark (?) or the exclamation point (!) provide a very broad-brush clue about the main intonational contour.

Supplemental information is usually isolated from the surrounding phrases by relatively longer syntactic pauses, whereas essential information is usually delivered as a contiguous syntactic unit.

Let's consider slightly different versions of your original sentence.

My brother in Canada is an architect.

This implies that the speaker has more than one brother. The architect is the one who is in Canada. "In Canada" is a reduced restrictive clause. It is an essential piece of information to identify which brother the speaker has in mind.

The sentence would be spoken:

{My brother in Canada} is an architect.

That is, the subject-phrase would be more-or-less contiguous, a unit, with no syntactic pause separating "my brother" and "in Canada".

My brother, who is in Canada, is an architect.

In this textual snippet of speech, the speaker is adding some extra information: My brother happens to be in Canada at the moment. There is no implication that he has more than one brother.

Now, if we leave out the commas:

My brother who is in Canada is an architect.

we are back to a full (not a reduced) restrictive clause: the speaker has more than one brother and wants to make clear that the architect is the one in Canada. The absence of commas reflects that fact that the isolating pauses that accompanied the extra information are absent in this speech, that is, the speaker is providing essential, not supplemental, information.

In actual speech, it would typically include some extra cues:

My brother who's in CANada is an architect.

The first syllable of Canada would typically receive extra stress. But punctuation, like musical notation, takes a minimalist approach, and provides analogues for only a narrow range of speech features.


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