Comma before the word 'which'?

[Enlightenment]

Hi,

I'm new to this forum, and if possible, would like some help.
I'm sorry if this question has been asked before, however, I still don't quite understand the use of a comma before the word which.

I'm currently studying for my year 2 in crystal healing, and I have a lot of written work to do. I need to know if it's necessary to put a comma before the word which in these two sentences?

There are a number of theories on what crystal therapy is and how it works. Here I will describe the two theories, which resonate with me the most.

One theory on how crystal-healing works is that of piezoelectricity. This is an electrical pulse, which emanates from the crystal in response to applied pressure.

[FONT=&quot]Thank you kindly!
[/FONT]

 

[Route21]

Hi Enlightenment

I believe what you are trying to say is actually:
This [i.e. piezoelectricity] is an electrical pulse that emanates from the crystal in response to applied pressure".

Commas aren't appropriate when "that" is the word to use.

Hopefully someone with better grammar expertise than mine will be able to explain the subtleties of the grammar involved.

Hope this helps
R21

 

[Enlightenment]

Hi Enlightenment

I believe what you are trying to say is actually:
This [i.e. piezoelectricity] is an electrical pulse that emanates from the crystal in response to applied pressure".

Commas aren't appropriate when "that" is the word to use.

Hopefully someone with better grammar expertise than mine will be able to explain the subtleties of the grammar involved.

Hope this helps
R21

Thank you for you help

I did wonder whether to change the word which to that. This also confuses me lol.
I never knew how complicated grammar could be Don't even get me started on the semi-colon, its been my nemesis throughout the whole of my year 2 studies.

Thanks again!

 

[5jj]

1. Here I will describe the two theories, which resonate with me the most.

2. This is an electrical pulse, which emanates from the crystal in response to applied pressure.

Route 21 was partly right.

In #1, the clause "which resonate with me the most" is essential to the sentence - it defines which theories you are talking about. In such 'defining' relative clauses, you can (but do not have to) use 'that' instead of 'which, and you must not separate it from the main clause by a comma.

There are two possibilities for #2:
Either:
a) It is a defining relative clause, telling us exactly which electrical pulse we are talking about. In that case, we can, if we wish, use 'that' instead of 'which', and we must not use a comma.
Or:
b) It is a 'non-defining' relative clause; we know that the electrical pulse is, we are simply giving additional information about it. The clause "which emanates from the crystal in response to applied pressure" could almost be placed between brackets (...). In that case we can use only 'which', not 'that', and we must use a comma.

 

[Enlightenment]

Route 21 was partly right.

In #1, the clause "which resonate with me the most" is essential to the sentence - it defines which theories you are talking about. In such 'defining' relative clauses, you can (but do not have to) use 'that' instead of 'which, and you must not separate it from the main clause by a comma.

There are two possibilities for #2:
Either:
a) It is a defining relative clause, telling us exactly which electrical pulse we are talking about. In that case, we can, if we wish, use 'that' instead of 'which', and we must not use a comma.
Or:
b) It is a 'non-defining' relative clause; we know that the electrical pulse is, we are simply giving additional information about it. The clause "which emanates from the crystal in response to applied pressure" could almost be placed between brackets (...). In that case we can use only 'which', not 'that', and we must use a comma.

Thank you for the detailed reply

I think I get what you're saying. So, when you say we shouldn't use a comma, do you mean if I use the word that, or if I use the word which? As I understand it, if I use the word that, instead of which, then no, I shouldn't use a comma.

Sorry to be a pain, grammar isn't my strong point.

 

[Enlightenment]

Ignore my last post. I've just re-read your post and I get it now, it makes sense Thank you.

 

[Route21]

Hi fivejedjon

Following on from your last point (and bearing in mind that the second sentence is actually the definition of piezoelectricity), if we were to combine the two sentences, could they read:

"One theory on how crystal-healing works is that of piezoelectricity, which is an electrical pulse that emanates from the crystal in response to applied pressure."

and/or

"One theory on how crystal-healing works is that of piezoelectricity (an electrical pulse that emanates from the crystal in response to applied pressure)."

Best regards
R21

 

[Enlightenment]

Hi fivejedjon

Following on from your last point (and bearing in mind that the second sentence is actually the definition of piezoelectricity), if we were to combine the two sentences, could they read:

"One theory on how crystal-healing works is that of piezoelectricity, which is an electrical pulse that emanates from the crystal in response to applied pressure."

and/or

"One theory on how crystal-healing works is that of piezoelectricity (an electrical pulse that emanates from the crystal in response to applied pressure)."

Best regards
R21

Argh, that sounds better I like the first one. Thanks for the input.

Does anyone else on here find they can become OCD with grammar? I'm thinking I've got 'grammar and punctuation OCD' lol. I really want everything to be perfect, though I'm finding that kind of difficult :-(

 

[5jj]

"One theory on how crystal-healing works is that of piezoelectricity, which is an electrical pulse that emanates from the crystal in response to applied pressure."

and/or

"One theory on how crystal-healing works is that of piezoelectricity (an electrical pulse that emanates from the crystal in response to applied pressure)."

They sound fine to me.