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The conditional in English

Clauses with if or unless

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Clauses with if or unless

Definition of a conditional clause

A conditional clause is a type of subordinate clause, most commonly introduced by the conjunction if or unless.  Like most subordinate clauses introduced by a conjunction, the conditional clause can either go before the main clause, or after it.

There are three types of conditional statement in English:

  1. Open conditional   as in If you want, you can go home.
  2. Hypothetical conditional  as in  If you wanted, you could go home.
  3. Unfulfilled hypothetical  as in  If you had wanted, you could have gone home.

Part 4:   Omission of "if".  and  Uses of whether

Type 1. Open if clause - the open conditional statement :

This usually refers to a future event which is conditional on another future event.
The verb of the main clause is in the future tense with "will" (or sometimes another modal) and the verb of the conditional clause is in the simple present tense. - examples 1 & 2.
But when the open conditional statement describes one perrmanent state of reality or circumstance which is dependent on another, in this case, both verbs are in the present tense - examples 3 - 5. (In such cases, if can be replaced by when.)

If the open conditional refers to past time (example 6) , then both verbs are in the simple past tense ; alternatively the past with would can be used in the main clause, but not in the if clause (and , if can be replaced by when.)
  1.  If you have a coffee this evening after dinner, you won't sleep well.  
  2.  If the temperature falls below zero tonight, it will freeze.
  3.  If (when) I sleep well at night, I feel much happier next morning.
  4.  If (when) the temperature falls below zero, it freezes.
  5.  If (when) it rains, everyone gets wet.   
  6.   If (when) he shouted too much, nobody listened (would listen).
In an open conditional statement, if is sometimes replaced by when: but there is a difference. Using "if" implies that the condition really is open and may not be fulfilled, using "when" implies that the condition will be fulfilled, that the event will really take place.

Type 2 if clauses - the open hypothetical conditional statement:

This refers to a possible future situation which depends on on another possible future situation. The verb of the main clause uses the present conditional tense (would + infinitive, or could +infinitive);
The verb of the conditional clause normally uses the present subjunctive or preterite (these two tenses are identical except with to be). Occasionally, the conditional aspect of the statement can be emphasised by using the form were + to + infinitive.
  •  1A  If you ate too much, you'd (you would) get fatter.
  •  1B  You'd get fatter if you ate too much.
  •  2A  If everyone worked faster, we would / could finish in time.
  • 2B  We wouldn't finish in time unless everyone worked faster.
  • 2C  If everyone were to work faster, we would/could finish in time.
  • 3    If I went to London, I would / could visit the British Museum.
  • 4.   If you visited Scotland, you could see Edinburgh Castle.
  • 5    Unless the directors increased sales, we'd have to close this shop.
Note also this common expression (which uses the open hypothetical form, though it is clearly quite impossible!)
  •       6.   If I were you, I'd ..........   
  • As in:  If I were you, I'd go a bit slower  
    or    If I were you, I'd put that gun down !!

This form is also used in cases of reported speech.
  • My professor told me I'd do much better if I worked harder.
  • The magistrate informed him that he'd go to prison unless he stopped stealing.
  • The newspaper reported that unless the directors could increase sales, they'd have to close the shop.

Type 3 if clauses - the unfulfilled hypothesis 

This refers to a situation which an event might have taken place, but did not, because a condition was not fulfilled.
The verb of the main  clause goes in the past conditional (would have + past participle).
The verb of the conditional clause goes in the past perfect (had + past participle).
  • If you had eaten too much, you'd (you would) have got fatter.
  • You'd have got fatter if you'd eaten too much.
  • If everyone had worked fast, we'd have finished in time (but we didn't).
  • We wouldn't have finished in time unless everyone had worked fast (but we did).
  • If I had gone to London, I could have visited the British Museum (but I didn't).
  • If you had visited Scotland, you could have visited Edinburgh Castle (but you didn't).
  • Unless we'd been very confident of success, we wouldn't have even tried.   (But we were confident, we did try, and we succeeded).

Note: using " unless"

"Unless" means the same as "if ... not", and has a negative value. It is frequently (but not only) used in conditional statements where the verb of the main clause is also  in the negative.
  • You wouldn't have fallen over unless there'd been a banana skin on the ground.
  • =   You wouldn't have fallen over if there hadn't been a banana skin on the ground. 

4a  Omission of "if", with inversion.

Sometimes, hypothetical conditional statements or unfulfilled hypothetical statements can be expressed omitting the word if.  
When this happens the subject follows the auxiliary verb in the conditional clause
  •  Were the virus to reappear, hospitals would now be ready for it. (open hypothesis)
  •   =   If the virus reappeared, hospitals would now be ready for it.
  •   or  If the virus were to reappear, hospitals would now be ready for it.

  •  Had I known, I'd never have gone there (unfulfilled hypothesis; implying "I did go there because I did not know".)
  •   =  If I had known, I'd never have gone there.

4b  Whether

Whether can sometimes replace if, when there is a choice of conditions. It implies
  1. a stated choice between two options (example 1, using whether... or) ,
  2. or a choice between an affirmative option and a stated negative option  (examples 2) ,
  3. or a choice between an affirmative option and an implied or stated  negative option in an indirect question (example 3).
See correlating coordinators

1.  I'll be there on time whether I come by train or I drive
2a.  He wants to go to the ceremony whether he's invited or not.
2b.  He wants to go to the ceremony whether or not he's invited.
3. I wonder whether it will rain tomorow (or not).  
In examples 1 and 2a, it would not be usual to use if in place of whether.
In example 2b, whether must be used. It is very unusual to say or write  "if or not"
In example 3,  there is a free choice between whether and if. Both can be used, though whether is preferred when followed by if not.

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