On Server Fault, we were discussing this question in chat. There are non-native speakers in the chat and somehow we got on the topic of grammar and proper use of commas.

The sentence of interest:

I have just got a new Ubuntu LAMP VPS server, which I am trying to configure.

Some people thought that the comma was superfluous. Others did not.

When is it appropriate for a comma to preceed the word which, and is the example sentence above correct?

Also, before you vote to close this question as a dupe of this, please consider the differences between the two questions and ignore the similarity of the titles. The OP's example sentence was restructured in that question instead of addressing the proper use of commas.

  • For what it's worth I'm on the side of "technically correct, but bad form in context" ("which" is a conjunction, and I'm trying to configure [the server] can stand alone as an independent clause, but the full thought it "I am trying to configure this new server"). I'm not an expert though, and I'm interested in everyone's thoughts. – voretaq7 Jan 12 '12 at 18:55
  • MDMarra, were you on the correct side of the argument, and which side won? – Marcus Adams Jan 12 '12 at 19:53
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    @MarcusAdams I thought that the comma belonged there. So far, it seems the community agrees with Barrie, which would put me on the winning side. :) – MDMarra Jan 12 '12 at 19:57
  • Does a the answer exist to this question at all?! [I'm prompted to ask, after reading the answers so far]. I thought I was very clear about it. – Kris Jan 13 '12 at 5:23
  • possible duplicate of Confused with the interpretation of the restrictive relative clause – MetaEd Jan 19 '12 at 15:30

Supplementary (or non-defining, or non-restrictive) relative clauses are by convention set off by commas and integrated (or defining, or restrictive) relative clauses are not. The clause in the example, 'which I am trying to configure', is a supplementary relative clause, so the comma is appropriate.

You can generally distinguish a supplementary relative clause from an integrated one by seeing whether or not you can detach the relative clause and still be left with a meaningful sentence. With the example, you can say simply 'I have just got a new Ubuntu LAMP VPS server' without the clause 'which I am trying to configure', which is a piece of bonus information. However, if the example had been 'I'm not getting anywhere with that new Ubuntu LAMP VPS server which I am trying to configure' the relative clause is essential in identifying exactly which new Ubuntu LAMP VPS server is being discussed. 'I'm not getting anywhere with that new Ubuntu LAMP VPS server' on its own doesn't tell us.

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    Thanks, Barrie; right on. This also ties in with the that/which issue, of course. – John Lawler Jan 12 '12 at 19:30
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    @JohnLawler: On which there appears to be something of a transatlantic divide. – Barrie England Jan 12 '12 at 19:35
  • @BarrieEngland I’m not sure that there’s really a pondian discrepancy there. Are you saying that it’s more acceptable to use ‘…server which I am…’ eastside of the pond, and that westside it would have to be written ‘…server that I am…’? I kinda thought those were just loose/general guidelines, not prescriptive rules, as there exist no shortage of examples from respectable writers sometimes using which for a restrictive clause — and not just ‘that which I tell you…’ stuff, either. That said, I might be careful of it myself, if only just to fend off the hypercorrections that it might trigger. – tchrist Jan 12 '12 at 20:28
  • I was thinking it should have been "On which, there appears to be something of a transatlantic divide.", with a comma. ! – Kris Jan 13 '12 at 5:21
  • @Kris: In supplementary relative clauses the comma comes before the relative pronoun, not after it. If the sentence had been 'That's a question on which there appears to be something of a transatlantic divide', there would still be no commmas at all because the clause 'on which . . .' is integrated. – Barrie England Jan 13 '12 at 8:18

Follow this rule:

  • If the 'which clause' is a defining clause, then no comma is required.
  • If the 'which clause' is not a defining clause, then the comma is required.

In the OP's sentence, the 'which clause' is non-defining so the comma is needed.

Here are some examples of defining 'which clauses':

  • The computer which I bought yesterday has broken down already.
  • Do you have the screwdriver which you borrowed last week?

Another way to think of a defining 'which clause' such as those above is that it identifies its antecedent.

  • Which computer has broken down? - the computer which I bought yesterday?
  • Which screwdriver are you talking about? - the one which you borrowed last week

Non-defining 'which clauses', on the other hand, do not identify the antecedent but give extra information about it:

  • My new computer, which I bought on Amazon, has broken down already.
  • My favourite screwdriver, which is a Philips, has gone missing.
  • I have just got a new Ubuntu LAMP VPS server, which I am trying to configure.
  • Can I simply just replace the 'which' with 'that' for all the sentences which have defining clauses in above examples? Defining clause means restrictive clauses? – user963241 Dec 23 '18 at 8:00
  • @user963241. Yes, you can replace which with that in restrictive (or defining clauses). In fact, some style guides prescribe that for restrictive and which for non-restrictive clauses. (Americans are more likely to abide by this 'rule' than Britons.) Note that if the relative pronoun is the object of the restrictive relative clause, then which / that can be omitted: The computer I bought yesterday doesn't boot or Please return the screwdriver you borrowed last week. – Shoe Dec 23 '18 at 9:14

You put a comma before which when there is only one new Ubuntu LAMP VPS server. If there is more than one, then the comma isn't used.

The logic behind this is that it all depends whether you need to differentiate the object you are talking about from another one with common traits. If you do, then the comma isn't used. In this case you can replace which with that. The information which follows which/that is necessary for the reader to understand which new Ubuntu LAMP VPS server you are talking about. If, however, there is no need to distinguish the servers because there is only one, you use comma before which and that can't be used in its place.

  • So you are saying that if the sentence was "I have two new Ubuntu LAMP VPS servers which I need to configure." there is no comma needed? – MDMarra Jan 12 '12 at 19:10
  • @MDMarra: No. Your sentence in the question is correct as long as there is only one new Ubuntu LAMP VPS server. If you have more than one, you must remove the comma. – Irene Jan 12 '12 at 19:14

"which" gets a comma; "that" does not. "I have just got a new Ubuntu LAMP VPS server that I am trying to configure."

  • I asked a two part question. I appreciate the response to the second part, but are you able to address the first part? My entire question is: When is it appropriate for a comma to preceed the word which, and is the example sentence above correct?" – MDMarra Jan 12 '12 at 19:02

protected by tchrist Mar 1 '15 at 18:52

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