The Definitions of Sentences
What expressed in the main clause, it depends – or is conditional – on what
expressed in the subordinate if clause; I will turn on the heating if it gets colder.
The if clause can come first or last in the sentence with no change in meaning. Notice that when the if clause comes first, it is followed by a comma;
If we did not have to study, we could go out tonight or we could go out tonight if we did not have to study.
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Here are alternates to if stating sort of conditions in
conditional sentences: a.
Negatives Conditions We often use unless to express a negative conditions. It is similar to if ... not
or only if: 1
Unless you have got a doctor’s note to say you have passed the medicine, they
will not allow you to go on the activity holiday.
If you do not have
a doctor’s note ..., they will not allow you ... 2
I would not be willing to help you out again unless you paid me.
I would help you only if you paid me.
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b. Necessary Conditions
We use the conjunctions providedproviding that, soas long as and on the condition that to emphasize that the condition is necessary to the result. They all
mean only if: 1
The system will not have to be drained provided that antifreeze has been
added. 2
Expenses will be reimbursed on the condition that all receipts are submitted.
To express a necessary condition for something to have happened in the past, we use but for + noun phrase:
3
They would have all perished, but for the quick thiniking of the driver.
... if it had not been for the quick thinking of the driver.
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Michael A. Ple and Mar Munoz Page, TOEFL Preparation Guide, New Jersey: Cliffs Publishers, 1994, p. 115.
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Mark Foley and Diane Hall, Longman Advanced Learner;’s Grammar....p. 123.
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Mark Foley and Diane Hall, Longman Advanced Learners ’ Grammar, .… p. 124.
c. Imaginary Conditions
We use supposesupposing that... and what if ... to talk about imaginary conditions.
1
Suppose he asked you to go to the cinema with him, would you go?
2
What if the money doesn’t arrive on time?
We often use in case to imagine a precaution necessary for a situation: 3
She gave me the key to get in the house in case you were out.
4
In case of an emergency, pull the cord above the bath.
d. Unexpected Conditions
We use even if to express a condition that is unexpected in the circumstances: