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Bracketing commas (also called isolating commas) do a very different
job from the other three types. These are the most frequently used type of
comma, and they cause more problems than the other types put together. The
rule is this: a pair of bracketing commas is used to mark off a weak interruption
of the sentence — that is, an interruption which does not disturb the smooth
flow of the sentence. Note that word `pair': bracketing commas, in principle at
least, always occur in pairs, though sometimes one of them is not written, as
explained below. Look carefully at these examples of bracketing commas:
In each case a weak interruption has been set off by a pair of bracketing
commas. (The last example has two weak interruptions.) Now notice
something important: in every one of these examples, the weak interruption set
off by bracketing commas could, in principle, be removed from the sentence,
and the result would still be a complete sentence that made good sense. Try this
with some of the examples:
- These findings, we would suggest, cast doubt upon his hypothesis.
- Schliemann, of course, did his digging before modern archaeology
- Pratchett has, it would seem, abandoned Rincewind the wizard to the
ravages of the Discworld.
- Darwin's Origin of Species, published in 1859, revolutionized
- The Pakistanis, like the Australians before them, have exposed the
shortcomings of the England batting order.
- Rupert Brooke, who was killed in the war at the age of 28, was one of
our finest poets.
- We have been forced to conclude, after careful study of the data, that the
proposed correlations, in spite of their obvious appeal, do not
This is always the case with bracketing commas, and it gives you a simple
way of checking your punctuation. If you have set off some words with a pair
of bracketing commas, and you find you can't remove those words without
destroying the sentence, you have done something wrong. Here is an example
of wrong use, taken from Carey (1958):
- These findings cast doubt upon his hypothesis.
- Pratchett has abandoned Rincewind the wizard to the ravages of the
- The Pakistanis have exposed the shortcomings of the England batting
- We have been forced to conclude that the proposed correlations do not
If you try to remove the words outside that door, the result is *Yet lay a whole
new world, which is not a sentence. The problem here is that outside that door
is not an interruption at all: it's an essential part of the sentence. So, the
bracketing commas shouldn't be there. Just get rid of them:
- *Yet, outside that door, lay a whole new world.
Here is another example:
- Yet outside that door lay a whole new world.
This time, if you try to remove the words and finding them, the result is *She
groped for her cigarettes hastily lit one, which is again not a sentence. The
problem is that the interruption in this sentence is only the sequence finding
them; the word and is not part of the interruption, but an essential
part of the
sentence. So move the first comma:
- *She groped for her cigarettes, and finding them, hastily lit one.
Now check that the interruption has been correctly marked off:
- She groped for her cigarettes and, finding them, hastily lit one.
This is a good sentence, so you have now got the bracketing commas in the
- She groped for her cigarettes and hastily lit one.
Since bracketing commas really do confuse many people, let's look at
some further examples:
What's wrong here? Well, that comma can't possibly be a listing comma, a
joining comma or a gapping comma; therefore it must be intended as a
bracketing comma. But where is the interruption it is trying to bracket? It can't
be the three words at the end: *Stanley was a determined is so much gibberish.
In fact, the weak interruption here is the phrase even ruthless, and the
bracketing commas should show this:
- *Stanley was a determined, even ruthless figure.
This is perfect, since now the bracketed interruption can be safely removed:
- Stanley was a determined, even ruthless, figure.
Sometimes this very common type of mistake will not disturb your reader too
much, but on occasion it can be utterly bewildering:
- Stanley was a determined figure.
Here the sequence before the comma, The Third Partition of Poland was the
last, seems to make sense by itself, but unfortunately not the sense that the
writer intends. With only one comma, the reader will surely assume the writer
means `The Third Partition of Poland was the last [partition of Poland]', will go
on to assume that the word undoubtedly begins another statement, and will be
left floundering when she abruptly comes to a full stop instead of a verb. The
essential second bracketing comma removes the problem:
- *The Third Partition of Poland was the last, and undoubtedly the most
humiliating act in the sorry decline of the once-powerful
Here is another example of a type which often causes trouble:
- The Third Partition of Poland was the last, and undoubtedly the most
humiliating, act in the sorry decline of the once-powerful
As always, we could in principle remove the bracketed interruption to produce a
- The people of Cornwall, who depend upon fishing for their livelihood,
are up in arms over the new EC quotas.
But note carefully: this sentence is talking about all the people of Cornwall, and
not just some of them, and hence so was the original sentence. The weak
interruption in the original sentence is merely adding some extra information
about the people of Cornwall. Now consider this different example:
- The people of Cornwall are up in arms over the new EC quotas.
This time their are no bracketing commas because there is no interruption: now
we are not talking about all the people of Cornwall, but only about some of
them: specifically, about the ones who depend upon fishing for their livelihood.
Here the phrase who depend upon fishing for their livelihood is not an
interruption but an essential part of the sentence, and hence it receives no
- The people of Cornwall who depend upon fishing for their livelihood
are up in arms over the new EC quotas.
Sometimes a weak interruption comes at the beginning or at the end of
its sentence. In such a case, one of the two bracketing commas would logically
fall at the beginning or the end of the sentence — but we never write a comma
at the beginning or at the end of a sentence. As a result, only one of the two
bracketing commas is written in this case:
When the weak interruption all in all comes at the beginning of the sentence, it
has only a following comma; when it comes at the end, it has only a preceding
comma. Compare what happens when the interruption comes in the middle:
- All in all, I think we can say that we've done well.
- I think we can say that we've done well, all in all.
Now the interruption has two bracketing commas. Regardless of where the
interruption is placed, it could be removed to give the perfectly good sentence
think we can say that we've done well.
- I think we can say that, all in all, we've done well.
Here are some further examples of weak interruptions that come at the
beginning or at the end.
At the beginning:
And at the end:
- Having worked for years in Italy, Susan speaks excellent Italian.
- Unlike most nations, Britain has no written constitution.
- Although Mercury is closer to the sun, Venus has the higher surface
- After capturing the Aztec capital, Cortés turned his attention to the Pacific.
Once again, the words set off by a single bracketing comma in these examples
could be removed to leave a good sentence. Check this for yourself.
- The use of dictionaries is not allowed, which strikes me as
- The pronunciation of English is changing rapidly, we are told.
- The Rose Parade is held in Pasadena, a suburb of Los Angeles.
There are a number of common words which typically introduce weak
interruptions containing complete sentences. Among the commonest of these
are although, though, even though, because, since
, after, before, if, when and
whenever. Weak interruptions introduced by these words are usually rather
long, and therefore they most often come at the beginning or at the end of a
sentence. Some examples:
There is just one case in which you might find yourself apparently
following all the rules but still using bracketing commas wrongly. Consider the
following example, and try to decide if the comma is properly used:
- Although Australian wines are a fairly new phenomenon, they have
already established a formidable reputation.
- After the Roman legions withdrew from Britain, the British found
themselves defenceless against Irish and Viking raids.
- If there are any further cuts in funding, our library will be severely
- Hitler could never have invaded Britain successfully, because their
excellent rail system would have allowed the British to mass
defenders quickly at any beachhead.
- Columbus is usually credited with discovering America, even though
the Vikings had preceded him by several centuries.
The comma in this example is clearly not a listing comma, a joining comma or a
gapping comma. Is it a bracketing comma? Try removing the words before the
- Note that in each of these examples, the material set off by commas
could be removed without destroying the sentence.
This appears to be a good sentence, and so you might think that the original
example was correctly punctuated. But it is not. The problem is that the
original sentence was an instruction to notice something, and the words Note
that are therefore an essential part of the sentence, not part of the interruption.
The interruption, quite clearly, consists only of the words in each of these
examples. When we tried to remove the first seven words, we got something
that was a sentence, purely by accident, but a sentence in which the original
meaning had been partly destroyed. The original attempt at punctuating was
therefore wrong, and it must be corrected by adding the second bracketing
comma around the interruption:
- The material set off by commas could be removed without destroying
Now the interruption marked off by the bracketing commas can be safely
removed without wrecking the sense of the sentence:
- Note that, in each of these examples, the material set off by commas
could be removed without destroying the sentence.
Therefore, when you are checking your bracketing commas, make sure
that the words enclosed in commas really do make up an interruption, and do
not include an essential part of the sentence.
- Note that the material set off by commas could be removed without
destroying the sentence.
In many cases a weak interruption does not absolutely require
bracketing commas. Thus either of the following is fine:
With or without the bracketing comma, this sentence is perfectly clear.
Sometimes, however, the bracketing comma is absolutely essential to avoid
misleading the reader:
- Shortly before the war, he was living in Paris.
- Shortly before the war he was living in Paris.
Here the reader naturally takes Just before unloading the trucks as a single
phrase, and is left floundering as a result. A bracketing comma removes the
- *Just before unloading the trucks were fired upon.
The best way to avoid problems of this sort is, of course, to read what you've
written. Remember, it is your job to make your meaning clear to the reader.
The reader should not have to struggle to make sense of what you've written.
- Just before unloading, the trucks were fired upon.
Here are the rules for using bracketing commas:
- • Use a pair of bracketing commas to set off a weak
interruption which could be removed from the
sentence without destroying it.
- • If the interruption comes at the beginning or the end of
the sentence, use only one bracketing comma.
- • Make sure the words set off are really an interruption.
Copyright © Larry Trask, 1997