The answer is in the root of the word. 'Conditional' is formed from 'condition'. One definition of 'condition' is: 'Something that is essential for something else to happen.' So every conditional actually says 'If this happens, then that will happen as well.' There are different types of conditional, because we use different grammar to say how likely it is that something will happen in the first place.
So, if you understand this, we can continue.
If you study English, you need to know about conditionals.
When you read this sentence, you must ask yourself a question. 'Do I study English?' The answer for some people might be 'no', but for you it is 'yes'. And because the first part of the conditional - the 'study English' is true, the second part is true as well. You do need to know about conditionals.
If I won the lottery, I would buy a helicopter.
With this example, the question is 'Will I win the lottery?' The answer is probably 'no'. So will I buy a helicopter? Probably not. However, the conditional in the sentence says that maybe I will win the lottery, maybe I won't. But even though it is unlikely I will win the lottery, it is certain that if I do win the lottery, I will buy a helicopter. With the conditional, you are saying that if the first part happens, even if it's very unlikely to happen, then the second part will certainly happen too.
Conditionals also work the other way around
If your English is perfect, you can stop reading now.
So ask yourself, 'Is my English perfect?' No? Then the first part of the conditional is not true, so the second part is not right either. Keep reading!
There are two parts to the conditional. One is called the 'if clause'. The 'if clause' talks about things that might happen. These things might be very likely to happen, or they might be improbable, or even impossible. Here are some examples of 'if clauses'
If the baby wakes up while I am out ...
If I buy a new car ...
If aliens landed on earth ...
If I were ten years younger ...
Some of these things may never happen. But the 'result clause' will always happen if the 'if clause' happens. The 'result clause' is a consequence of the 'if clause', and the grammar of the conditional says that the 'result clause' must happen if the 'if clause does'. Here are the sentences with the 'result clause' added.
If the baby wakes up while I am out, he will start to cry.
If I buy a new car, it will be a Rolls-Royce.
If aliens landed on earth, life would change forever.
If I were ten years younger, my sister would be older than I.
The two clauses can come in any order. You can start with the 'result clause' (for dramatic emphasis), or with the 'if clause'. If there is a pronoun in the second clause, and you change the order of the clauses, you should still make the pronoun come after the subject noun. So here are the sentences with the clauses changed around.
The baby will start to cry if he wakes up while I am out.
My new car will be a Rolls-Royce, if I buy one.
Life would change forever if aliens landed on earth.
My sister would be older than I if I were ten years younger.
Did you notice that if the result clause comes first in a short sentence, you don't use a comma? That's right. You don't use a comma if the result clause comes first in a short sentence.
There are three basic types of conditionals.
First conditionals deal with things that are very likely to happen.
If Bill sees you tomorrow, he will ask you to call me.
Notice that when the 'if clause' has a future meaning we still do not use 'will'. However, you use future in the 'result clause'. If the 'if clause' is present we can use present or future in the 'result clause' depending on what we want to say.
If it is so easy, you can do it yourself.
If it is only a kilometer to town, we will be there before lunch.
However, if you can use 'when instead of 'if' and use present tenses for both clauses you have what is sometimes called a Zero Conditional for something that happens often and always in the same way.
If you heat water enough, it boils.
Can be re-written as
When you heat water enough, it boils.
The Second conditional talks of things that probably won't happen. When we talk of probabilities we use a particular 'mood' called the subjunctive. For now, we can consider subjunctives in conditionals as being rather like past tenses. (Although the meaning is different, the grammar is almost the same).
Look at the example If Bill sees you tomorrow, he will ask you to call me.
Maybe Bill is on another continent, and it is not likely you will see him tomorrow. I can show that I do not think this will happen by changing the structure of the conditional.
If Bill saw you tomorrow, he would ask you to call me.
We can also write this as an 'explicit subjunctive' and say
If Bill were to see you tomorrow, he would ask you to call me.
Because things in the present or future might always be possible, we use second conditionals even for things that we are nearly 100% certain will not happen.
If I was ten years younger, I might enjoy his company.
The third conditional is sometimes called the 'impossible' conditional, because it talks of events in the past. Things in the past cannot be changed, but we sometimes like to imagine what would have happened if the past had been different.
If I had not robbed the bank, I would not be in jail today.
The third conditional uses a past perfect in the 'if clause' and 'would have' in the 'result clause'.
If you had taken the car, you would have got there quickly.
If this explanation is too simple for you, look at the grammar of the conditional in the advanced section. On the other hand, you should read the grammar in the elementary section if this seems too difficult. If the level seems right, then we can do some exercises.