関係代名詞の使い方, part 9: comma or no comma?

I'm continuing my series on relative pronouns. A complete list of the posts which are about relative pronouns is at the end of this post.

Like I said late Friday night, the key point about using a comma or not is related to the word "essential". If the relative clause is essential to the meaning of the sentence, you cannot use commas. If the relative clause is nonessential to the meaning of the sentence, you must use commas.

To say it in another way, if you can leave out the relative clause without changing the meaning of the sentence, use commas. If you change the meaning of the sentence when you leave out the relative clause, don't use commas.

• 除く (のぞく) (v5k,vt) to remove; to exclude; to except; to omit; to leave out;

On Friday, I asked you about these sentences:

• The picture which I have posted today is of my ancestors. <- essential information

Look at the version without the relative clause:

• The picture is of my ancestors. <- which picture? The meaning is not clear.

How about this one?

• The pictures were gathered by my uncle, who lives in Georgia now. <- nonessential information
• The pictures were gathered by my uncle. <- the meaning is still clear

Here are the sentences from yesterday's post:

• The vegetable soup which is in this picture wasn't nearly as delicious as the chickpea curry which I made for breakfast today.
• The vegetable soup wasn't nearly as delicious as the chickpea curry. <- which soup? which curry? These are essential relative clauses.
• My iPhone, which always makes me angry, didn't save the photo somehow. <- you know which iPhone. The relative clause is not necessary.

Go back and look at all of these sentences in yesterday's post and see if you understand why some of the relative clauses are essential and the others are not.

This is a photo of my bicycle, which I took last night. My bicycle, which had a flat earlier today, has become essential for me.

• have a flat tire パンクする Helen had a flat tire this morning, that's why she was late for work. : ヘレンは今朝、車がパンクしたので仕事に遅刻しました。(definition from 英辞郎 on the web)

Fortunately I was only a few blocks away from a place which could fix it. That was lucky! While I was there, I asked them to check my chain and my gears, which had been making a strange noise. Now my bike is in excellent condition, but it's still a bit dirty.

To review, here are all of the previous posts on relative clauses:

http://upgradeenglish.blogspot.com/2009/07/no.html
http://upgradeenglish.blogspot.com/2009/07/part-2.html
http://upgradeenglish.blogspot.com/2009/07/part-3.html
http://upgradeenglish.blogspot.com/2009/08/part-4-that.html
http://upgradeenglish.blogspot.com/2009/08/part-5-who-which-where.html
http://upgradeenglish.blogspot.com/2009/08/part-6-where.html
http://upgradeenglish.blogspot.com/2009/08/part-7-comma-or-no-comma.html
http://upgradeenglish.blogspot.com/2009/08/part-8-comma-or-no-comma.html