英语小镇

17-7 Adverb clause of Condition: Using in case and in the event that
(a) I'll be at my uncle's house in case you (should) need to reach me. (b) *In the event that* you (should) need to reach me, I'll be at my uncle's house.	*In case* and *in the event that* express the idea that something probably won't happen, but it might. *In case/ in the event that* means "if by chance this should happen." Notes: *In the event that* is more formal than *in case.* The use of should in the adverb clause emphasizes the speaker's uncertainty that something will happen.
17-8 Adverb clauses of condition: Using unless
(a) I'll go swimming tomorrow unless it's cold. (b) I'll go swimming tomorrow if it isn't cold.	Unless = if...not In (a): unless it's cold means "if it isn't cold." (a) and (b) have the same meaning.
17-9 Adverb clause of condition: Using only if
(a) The picnic will be canceled only if it rains. If it's windy, we'll go on the picnic. If it's cold, we'll go on the picnic. If it's damp and foggy, we'll go on the picnic/ If it's unbearable hot, we'll go on the picnic.	*Only if* expresses the idea that there is only one condition that will cause a particular result.
(b) Only if it rains will the picnic be canceled.	When only if begin a sentence, the subject and verb of the main clause are inverted, as in (b). No commas are used.
Other subordinating conjunction and prepositional phrases fronted by only at the beginning of a sentence require subject-verb inversion in the main clause: (1) *Only when* the teacher dismisses us can we stand and leave the room. (2) *Only after* the phone rang did I realize that I had fallen asleep in my chair. (3) Only in my hometown do I feel at ease.
18-1 Reduction of Adverb Clauses to Modifying Adverbial Phrases: Introduction
(a) Adverb Clause: While I was walking to class, I ran into an old friend. (b) Modifying Phrase: While walking to class, I ran into an old friend. (c) Adverb Clause: Before I felt for work, I ate breakfast. (d) Modifying Phrase: Before leaving for work, I ate breakfast.	Some adverb clauses may also be changed to modifying phrases, and the ways in which the change are made are the same: 1. Omit the subject of the dependent clause and the be form of the verb , as in (b). Or 2. If there is no be form of a verb, omit the subject and change the verb to -ing, as in (d).
(e) Change Possible: While I was sitting in class, I fell asleep. While sitting in class, I fell asleep. (f) While Ann was sitting in class, she fell asleep. While sitting in class, *Ann* feel asleep.	An adverb clauses can be change to a modifying phrase. Only when the subject of the adverb clause and the subject of the main clause are the same. A modifying adverbial phrases that is reduction of an adverb clause modifies the subject of the main clause.
No Change Possible:> (g) While *the teacher* was lecturing to the class, I feel asleep. (h) While we were walking home, a frog hopped across the road in front of us.	No reduction is possible if the subjects of the adverb clause and the main clause are different, as in (g) and (h).
Incorrect: (i) While walking home, a frog hopped across the road in front of us. (j) While watching TV last night, the phone rang.	In (i): "While walking home is called a "dangling modifier" or a "dangling participle", a modifier that is incorrectly "hanging alone" without an appropriate noun or pronoun subject to modify.

18-2 Changing Time Clauses to Modifying Adverbial Phrases
Adverbial Phrases: (a) Clause: Since Maria came to this country, she has made many friends. (b) Phrase: Since coming to this country, Maria has made many friends.	Adverb clause beginning with *after, before, while,* and *since* can be changed to modifying adverbial phrases.
(c) Clause: After he (had) finished his homework, Peter went to bed. (d) Phrase: After finishing his homework, Peter went to bed. (e) After having finished his homework, Peter went to bed.	In (c): There is no difference in meaning between After he finished and *After he had finished* . In (d) and (e): There is no difference in meaning between After finishing and *After having finished*
18-3 Expressing the Idea of "During the Same Time" in Modifying Adverbial Phrases
(a) *While I was walking* down the street, I ran into an old friend. (b) *While walking* down the street, I ran into an old friend. (c) *walking* down the street, I ran into an old friend. (d) Hiking through the woods yesterday, we saw a bear. (e) *Pointing* to the sentence on the board, *the teacher* explained the meaning of modifying phrases.	Sometimes *while* is omitted but the *-ing* phrases at the beginning of the sentence gives the same meaning (during the same time) (a), (b), and (e) have the same weaning.
18-4 Expressing cause and Effect in modifying adverbial phrases.
(a) Because she needed some money to buy a book, Sue cashed a check. (b) *Needing* some money to buy a book, *Sue* cashed a check. (c) *Because he lacked* the necessary qualifications, he was not considered for the job. (d) *Lacking* the necessary qualifications, he was not considered for the job.	Often an -ing phrases at the beginning of a sentence gives the meaning of "because". (a) and (b) have the dame meaning. Because is not included in a modifying phrase. It is omitted, but the resulting phrase expresses a cause and effect relationship, as in (b) and (d)
(e) *Having seen* that movie movie before, I don't want to go again.	*Having* + past participle gives the meaning not only of "because" but also of "before".
(f) Because she was unable to afford a car, *she* bought a bicycle. (g) Being unable to afford a car, *she* bought a bicycle. (h) Unable to afford a car, she bought a bicycle.	A form of be in the adverb clause may be changed to *being. The used of being* makes the cause and effect relationship clear. (f), (g), and (h) have the same meaning.
*18-5 Using Upon + ing* in Modifying adverb**
(a) *Upon reaching* the age of 21, I received my inheritance. (b) When I reaching the age of 21, I received my inheritance.	Modifying adverbial phrases beginning with *upon + ing* usually have the same meaning as adverb clauses introduced by *when*. (a) an (b) have the same meaning.
(c) On reaching the age of 21, I received my inheritance.	Upon can be shortened to on . (a), (b), and (c) all have the same meaning.

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