Consider these expressions,

The article is about Mr X, who invented Y in 1960.

In this expression do I need a comma after Mr X?

I took a look at this document, It discusses Restrictive vs. Nonrestrictive Relative Clauses but I don't think my expressions are either one of those.

  • Well, I guess it depends on your audience. Do they know Mr. X and do they know he invented Y in 1960? Is Mr. X ambiguous or not? Is it important to know that Mr. X invented Y in 1960 or is this just actually worthless information?
    – Em1
    Commented Nov 4, 2013 at 13:38
  • @Em1 I get your point, but I don't think it is 'worthless' information. :)
    – Max
    Commented Nov 4, 2013 at 15:53

1 Answer 1


The general principle is that a non-restrictive clause should be set off by commas, while a restrictive clause should not. A restrictive clause is one that serves to identify the subject, while a non-restrictive clause is giving additional information about the subject.

So for example, suppose you and I have two friends named "Bob". One works at the hardware store and one works at the bank. If I wanted to tell you something about Bob, I might need to make clear which one. So I could say, "Bob who works at the bank just bought a new car." Sometimes when we use a restrictive clause like this we add "the" before the subject, as in, "The Bob who works at the bank just bought a new car."

On the other hand, if I wanted to tell you that Bob bought this car, and as a side note mention that he works at the bank, I would use a non-restrictive clause. "Bob, who works at the bank, just bought a new car." Usually we do this when the clause is specifically relevant. Like, "Bob, who works at the bank that was robbed last week, bought a new car the day after the robbery."

Whether a clause is restrictive or non-restrictive depends entirely on the intent of the writer and whether there is potential ambiguity without a restrictive clause.

In your example, it could depend entirely on how common the name is. "This article is about Mr Einstein, who invented the theory of relativity." Einstein's name is so well known that it is unlikely we need to make clear who he is. But, "This article is about Mr Einstein who invented the edible cell phone." Now we're talking about some Mr Einstein other than the one people would normally think of, so we need a restrictive clause to clarify that this is someone else.

  • +1, Thanks for your answer. Is this comma correct? "X opeartion will return a image, which I'll use to get the data in it." I feel like it is a non restricted phrase.
    – Max
    Commented Nov 4, 2013 at 17:07
  • Yes, assuming there is not some other image under discussion that it could be confused with. The sentence appears to be saying that you will use the image to get the data in, which doesn't make sense to me. If that is in fact what you mean, I don't need to understand the details of your computer system, so whatever. If that's not what you mean, the sentence may need to be reworded.
    – Jay
    Commented Nov 5, 2013 at 14:27
  • I mean, I want to capture the text inside the image with my system.
    – Max
    Commented Nov 5, 2013 at 16:16
  • Ah. Maybe surrounding text makes it clear. But when you say "which I'll use", the natural reading is that you will use the image to do something, not that you will do something with or to the image. I would say, "Operation X will return an image. I will then get the data from the image." or, "Operation X will return an image, from which I will get the data."
    – Jay
    Commented Nov 7, 2013 at 15:48

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .