Conditional sentences (also known as conditional clauses or if clauses) are made up of two halves. One half (the half with the word if in) is a condition, and the other half (the main clause) states the action to occur if the condition is fulfilled.
The Types of Conditional Sentence
There are three types of conditional sentence:
Conditional Sentence Type 1
Type 1 sentences are used when it is likely that the condition will be fulfilled. It is formed like this:
If you had swallowed some of the cleaning fluid, it would have killed you.
If I had had a little humility, I would have been perfect.
Using Commas in Conditional Sentences
When the condition is at the start of the sentence (like in all the examples above), it is usual to separate it from the main clause with a comma. However, if the condition is at the back of the sentence, it is less common to use a comma. (You can still use a comma to assist your reader if you think it aids understanding.)
It will kill you if you swallow some of the cleaning fluid.
I would have been perfect if I had had a little humility.
Forming Conditional Sentences (Graphical Summary)
Here is a graphical summary of the three types of conditional sentence: