First of all, we must understand that all these clauses refer to subordinate clauses.
To know more about clauses and subordinate clauses click here.
When a subordinate clause denotes a condition, then it is called as a Conditional clause.
eg: If you study well, you will get high marks.
Here, the example suggests a condition for you to get high marks, that is, you must study well.
We can understand that the given example is a complex sentence in which the subordinate clause , ” If you study well” denotes the condition and the main clause ” You will get high marks” anticipates the result of the condition. So, the subordinate clause in the example can be called as a conditional clause.
In grammar, conditions are classified into two types:- Likely and Unlikely conditions.
Conditions, possible to happen, are known as Likely conditions.
eg: If he learns grammar, he can use English correctly.
Here, the condition to learn grammar, mentioned in the subordinate clause “If he learns grammar”, is generally possible to happen. So this is supposed to be a likely condition.
Conditions, impossible to happen, are known as Unlikely conditions.
eg: If I were a bird, I would fly.
Here, the condition to be a bird, mentioned in the subordinate clause ” If I were a bird”, is impossible to happen, as far as I am concerned. So this is considered as an unlikely condition.
It is to be noted that when an unlikely condition is mentioned in past tense, the auxiliary verbs or verbs in the subordinate clause should be plural, even if the subject of the clause is singular in form. That is why the plural verb ‘were’ is used with the singular subject ‘I’ in the above given example.
When a subordinate clause refers to an imagination, then the subordinate clause is generally known as an Imaginary clause
eg: If I am rich, I will own a Jaguar.
Here, the example shows an imagination related to my state of being rich. So the subordinate clause is supposed to be an imaginary clause.
Whenever a subordinate clause begins with ‘If,’ then the subordinate clause, either denoting a condition or an imagination, can be called as an If clause.
eg: If he played well, he would win the match. ( a condition )
If he had been sachin, he could have scored the runs. ( an imagination )
That means conditional or imaginary clauses can commonly be called as If clauses .