CONDITIONAL CLAUSE 1

Type 1. 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).
The verb of the conditional clause is in the simple present tense. 

•      If you eat too much, you'll get fatter.
•      You'll get fatter if you eat too much.
•      If everyone works fast, we'll finish in time.
•      We won't finish in time unless everyone works fast.
•      If I go to London, I can visit the British Museum.
•      If you visit Scotland, you should visit Edinburgh Castle.
•      Unless the directors can increase sales, we'll have to close this shop.

Occasionally, the open conditional statement describes one potential state of reality or circumstance which is dependent on another.  In this case, both verbs are in the present tense.

•      If I sleep well at night, I feel much happier next morning.
•      If the temperature falls below zero, it freezes.
•      If it rains, everyone gets wet.   

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. 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.                                   

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