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English as a Second Language/When to use comma before which?

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QUESTION: Dear Amy,

I don't know why my messages are being erased. I have sent this question to you again. I am really confused on when to use comma before "which". Let's look at the following sentences:-

1a) She tried to separate me from her, which is not possible.

1b) She tried to separate me from her which is not possible.


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2a) The shoe is dirty which I bought from store.

2b) The shoe is dirty, which I bought from store.


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3a) He ignored her, which hurt her.

3b) He ignored her which hurt her.

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4a) He committed a crime which can not be justified in any way.


4b) He committed a crime, which can not be justified in any way.

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5a) The book which you took yesterday is lost.

5b) The book, which you took yesterday is lost.

5c) The book, which you took yesterday, is lost.

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6a) He is practicing, which is a good thing.


6b) He is practicing which is a good thing.

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7a) She disregarded my advice, which shocked me.


7b) She disregarded my advice which shocked me.


Respected Amy, is "which shocked me" an independent clause?

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I want to ask one more question that is the article "a" really needed in this sentence?


1) People who walk more have a better heart function than people who don't.


2) People who walk more have better heart function than people who don't.

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Thanks.

ANSWER: Hello Den,

I got your question, three times. Not sure what happens at your end, but I have received it and answered it already. I'll add here to my original answer as your latest version of the question is longer.


interesting question here, and not an easy one, I might add.

The use of a comma before "which" is a difficult topic even for some native speakers,but let me try to clarify things for you.


1a) She tried to separate me from her, which is not possible. >>> correct
1b) She tried to separate me from her which is not possible.

(She tried to separate me from her, and that is not possible)

2a) The shoe is dirty which I bought from store.
2b) The shoe is dirty, which I bought from store. >>> correct

(better yet: The shoe, which I bought from the store, is dirty.)

3a) He ignored her, which hurt her. >>> correct
3b) He ignored her which hurt her.

(He ignored her, and that hurt her.)

4a) He committed a crime which can not be justified in any way. >>> correct
4b) He committed a crime, which can not be justified in any way.

(He committed a crime that can not be justified in any way.)

5a) She disregarded my advice, which surprised me. >>> correct
5b) She disregarded my advice which surprised me.

(She disregarded my advice, and that surprised me.)

5a) The book which you took yesterday is lost.
5b) The book, which you took yesterday is lost.
5c) The book, which you took yesterday, is lost. >>> correct

6a) He is practicing, which is a good thing. >>> correct
6b) He is practicing which is a good thing.

(He is practicing, and that is a good thing.)

7a) She disregarded my advice, which shocked me. >>> correct
7b) She disregarded my advice which shocked me.

(She disregarded my advice, and that shocked me.)

"which surprised/shocked me" is a clause but not an independent one; it has an implied noun: (which) her action, and a verb: surprised/shocked, this makes it a clause.

When to use comma before which when not?

As a rule, if the information in the relative clause (the one starting with "which") is "restrictive" you don't need to use a comma there, if the info is not restrictive, then a comma should be used.

What do I mean by "restrictive" - the info in the clause is necessary to identify the person/thing it describes, it's not just some info you can remove.
If the info following "which" can be removed, yet the overall sentence doesn't lose meaning, then you need a comma before "which".

Fore more information regarding the proper use of commas before "which" please see the following sites:


http://www.grammar-monster.com/lessons/which_that_who_comma_or_not.htm

http://www.grammarly.com/answers/questions/17353-use-of-comma-before-which-and-b

http://www.grammar-monster.com/lessons/which_that_who_with_commas.htm

Feel free to follow up with me if you still have questions about this topic.

Best,

Amy

---------- FOLLOW-UP ----------

QUESTION: Dear Amy,

First of all thanks for your answer. I got a better picture of this subject. I just want to clarify that you said that If the info following "which" can be removed, yet the overall sentence doesn't lose meaning, then you need a comma before "which".

In the following sentence:-


4a) He committed a crime which can not be justified in any way.


4b) He committed a crime, which can not be justified in any way.


We can remove the second part of the sentence "can not be justified in any way." Yet we will have "He committed a crime". If we remove the second part, yet first part still has meaning: "He committed a crime." So, do we need a comma here? Or we don't need a comma here because it is a whole sentence? I also read that if any additional information which follows "which", then comma should be used before "which".  

Kindly clarify.


Thanks.

Answer
Den,

the sentence you're inquiring about is a bit tricky.

According to the rules, if the info in the clause introduced by "which" is NOT needed to identify the person/object/thing it describes, then you should use commas to offset that sentence.

Another way to put this: use a comma before "which", if "which" introduces a nonessential clause (a clause that adds info to the sentence but is not essential to the main point of the sentence).

Here you have a sentence that can actually go both ways depending on how you interpret it. In my opinion, "which can not be justified in any way" is essential info, so no comma is needed.

If you think that the second sentence is needed to identify the crime committed, then you don't use commas; if, in your opinion, you need the second sentence to identify the crime committed, then you don't use commas.

To clarify my original answer: I should have said "If the info following <<which>> can be removed, yet the overall sentence doesn't lose its ORIGINAL meaning, then you need a comma before <<which>>"

I hope this helps.

Again, I realize this is a confusing topic, and I just hope my answer didn't add to your confusion.

Best,

Amy

English as a Second Language

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Amy Baker

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