If the weather is fine this weekend, I´ll go skiing.
I.e. I´ll go skiing on condition that the weather is fine this weekend.
There are different types of conditional sentences depending on the meaning we intend to convey. So whether we need to show certainty, a possibility in the future, a hypothesis, or a regret about something that already happened, we will need to use one particular type of conditional sentence or another.
The conjunctions if, even if, when, whenever, whether, and unless (amongst others) often appear in conditional sentences.
As you can see, conditional sentences are not a simple matter and they need to be studied in detail.
In a previous post, I dealt with zero and first conditionals. Next, you´ll be able to have a look at a PowerPoint presentation where I try to clarify unreal conditionals (i.e. 2nd and 3rd types).
Now, try and practise what you´ve learnt by doing the following exercises:
Finally, try working with your conditionals by filling in the gaps in the song "If You Were a Sailboat", by the wonderful Katie Melua.
If you found it useful, I would be terribly happy!