One definition of a 'condition' is something which will not happen unless something else happens first. For example Fred may lend Jenny his bicycle 'on condition that' she helps him with his homework. So unless Jenny helps with Fred's homework, she can't borrow the bike. The simplest way of expressing a condition is with the word 'if'. So Fred may express his conditions for lending his bike as 'I will lend you my bike if you help me with my homework.' However, conditionals do not always use 'if'; for example 'on condition that' can be sometimes used instead in formal statements.
Conditionals are traditionally given as three types.
First conditionals - these describe possible events and what would happen after that event.
For example: If Manchester United win this game they will be top of the Premier League.
Second conditionals - these describe unlikely events which are possible but not probable.
For example: If my school soccer team beat Manchester United it would be in all the newspapers.
Third conditionals - these describe 'impossible' events (sometimes 'impossible' because they are in the past, and the past cannot be changed), but third conditionals still say what would have been the result if the impossible did happen or if the past had been different.
For example: We would have won if the referee had not been totally unreasonable and unfair.
To these is generally added another class of conditionals -
Zero conditionals
For example: If you hit your toe with a hammer, it hurts.
Zero conditionals and some first conditionals are also called Real conditionals, because unlike second and third conditionals they describe very probable - or even inevitable - events.
For example: If you laugh, you feel better. (You are going to laugh at some time, aren't you? So this event is not only probable, but certain.)
Real conditionals can be expressed in other ways.
For example: (positive) When you drive over that hill, you'll see the town.
For example: (negative) Unless you drive over that hill, you won't see the town.
Other constructions can have the same effect as Real conditionals
For example: (using 'and' for an inevitable effect) Drive over that hill and you'll see the town.
For example: (omitting 'if' completely) What does not kill you makes you stronger'.
These two sentences can be written as conditionals without changing the meaning:
If you drive over that hill, you'll see the town.
If something does not kill you, it makes you stronger.
However, although these other constructions are close in meaning to conditionals, their grammar is slightly different.
A Conditional has two types of clauses.
1. The If Clause.
(Language scholars prefer to call this 'the protasis', because, as we have seen, an 'if clause' need not contain an 'if'. However, we will use 'If Clause' in our description here.)
The If Clause always describes a situation or event, whether this event is real, imaginary or impossible, and uses any verb tense.
One of the grammatical definitions of a Conditional is that the If Clause and the Result Clause can come in any order.
For examples
If Manchester United lose this game, they will win the next one.
Manchester United will win the next game if they lose this one.
There are two things to note here
Firstly, when the If Clause comes first, it is usually separated from the Result clause by a comma.
Secondly, it is usual to put the nouns into the first clause and the pronouns into the second clause, (though sometimes this is not done as a 'reversal' makes the sentence more dramatic.)
The voice of the If Clause tells us about the probability of an event or if it is real.
The Indicative voice tells us a sentence is probable or real.
For examples
When it is sunny, I like to walk to work.
If I see my neighbour, I stop for a chat.
Conditionals can have their meaning altered, for example by adverbs.
For example, compare
We would have won the game if Fred had been on the team.
We would have won the game only if Fred had been on the team.
In the unmoderated conditional, if Fred had been on the team, it would have won. But there may have been other ways of winning - playing harder, bribing the referee, and so on. However adding the word 'only' to the second example removes these other alternatives - with Fred the team would have won, otherwise it was certain to lose.
A variation of 'only if' is 'if only'. The 'if only' construction is a special type of third conditional used to express regret about a situation and a wish for something impossible - such as a change in the past - which would sort out the problem. Quite often the Result Clause is left out, as the audience is expected to know what it would be.
For example, compare
If only I were twenty years younger.
If only I had a million dollars.
If only you had not forgotten our tickets and passports at the hotel.
With the 'if only' conditional, if the Result Clause is included, 'if' and/or 'only' can be left out when 'had' is moved to the start of the clause.
For examples
We would have won the game if we had only played better.
We would have won the game had we only played better.
We would have won the game had we played better.
'Even if' generally works the same way grammatically as 'if only', but has the meaning that the If Clause does not change the Result Clause (which is one reason why, as mentioned above, language scholars do not like to call it a 'Result clause'.)
For example We would have lost the game even if we had played better.
The meaning here is that the game would certainly be lost, and whether our team played well or badly could not have changed this. (Perhaps the other team had indeed bribed the referee.)
Another way of saying 'even if' is 'no matter'. 'Even if' is specific about what would have not changed the result and 'no matter' explains that (depending on the question word which follows) any person, action, time or thing would not have changed the result.
Compare
We would have lost the game even if Fred had been in our team.
We would have lost the game even no matter who was in our team.
Even if we had played yesterday, we would have lost the game .
No matter when we played, we would have lost the game .
We would have lost the game even if we had played better.
We would have lost the game no matter how we played.