非限定子句

限定子句

(1) My brother who lives in Taipei will come back next week.
“who lives in Taipei” 在你這句子中是限定子句
講者指明是居住台北那個兄弟, 不是其他的兄弟,其他的兄弟可能居住北美, 歐洲或者其他地方. 講者至少有兩個兄弟.
限定子句是不可缺少的子句, 用來識別 (identify) 那位兄弟, 不是任何一個, 所以限定子句是需要 (limiting, restricting = 限定)
英文稱 defining clause, (restrictive clause) – clause singles out a particular person or thing from two or more similar people or things, showing which one we are talking about.

我例子:
(2) Is this the book that you were looking for?
that you were looking for 是限定子句, 用來識別那本書, 不是任何一本, 是你之前找那本

非限定子句

(3) My brother, who lives in Taipei, will come back next week.
“who lives in Taipei” 在你這句子中是非限定子句, 前後有逗點
講者講有一個兄弟下星期回來, 這個兄弟居住台北
不限定子句可有可無, 不是一定需要, 作用是補充, 講多句關于兄弟, (additional information), 如果省略了, 無傷大雅, 不會影響主句原意 My brother will come back next week
講者可能有一個兄弟或者多個兄弟
英文稱 non-defining clause, (non-restrictive clause) – clause which doesn’t define in that particular context even though the same words in the same place, if spoken or punctuated differently, might do so.

我例子:
(4) My Uncle David, who is a classical music fanatic, is a surgeon.
“who is a classical music fanatic” 是非限定子句
classical music fanatic = 古典音樂狂熱者
My Uncle David would still be my uncle even if he were not a classical music fanatic. The information provided in the clause does not serve to tell us which uncle I am talking about. I only have one uncle. The fact that he is a classical music fanatic does not serve to distinguish one Uncle David from other. 所以是非限定 (non-restrictive).

非限定子句如果在整句中間, 前後有 commas 分開

其他你提到的gerund phrase, present participle phrase, infinitive phrase 是另外的話題, 有機會再討論, 用了你兩個例子和我兩個例子, 希望你能夠辨別限定子句與非限定子句, 何時用到. Good luck!

Dear Solo,
(1)Defining Clauses
Adjective clauses are of two types. Consider the following examples:-
My brother who lives in Taipei will come back next week.(=others)
In this sentence the adjective clause is a necessary part of the idea; If it is left out, the sentence does not make complete sense. All this clause define the antecedent and give it its definite notation significant.They indicate which brother out of many brothers.

(2)Non-definition clauses
Now consider this sentence:-
My brother, who lives in Taipei, will come back next week. (-only one)
In all this sentence the adjective clause could be omitted and the rest of the sentence would still make perfect sense.The adjective clauses here are a kind of parenthesis, a casual remark, an aside or an explanation. They could be written between brackets or dashes, eg:-
My brother (who lives in Taipei) comes.
My brother----who lives in Taipei-------comes next week.
They do not define the antecedent (=brother).
What they do is to give additional information about an antecedent which has already been sufficiently defined. They are therefore called NON-Defining or AMPLIFYING Clauses.
This parenthetical construction of non-defining clauses is shown by a comma in writing and by a pause in speaking at the beginning and end of the clause
NB,Commas must not be put round a defining clause(=other brothers)
NB:-Working as a life guard, he.....
means participles as adverb clause equivalents
workign=as, because he was working, as he worked.
Keep up your good work.

2014-03-06 09:14:07 補充：
(1)Subjects are different between front&back=independently:-The pool deck having cleaned, he slipped. This cleaning (being) done, he added chlorine. He acts as a lifeguard,work permitting. There being no lifeguard around, he slipped&sprained.
(2)Independent subjects at-Arriving 1 hr before...