Conditionals: the essentials

From "If" by Rudyard Kipling

Conditionals are a special form of sentences with a main and a subordinate clause (see the section on conjunctions in the word class area) which show how one event depends on another.  Here are a few examples:

1. If you see John, will you ask him?
2. I would not bother with it if I were you.
3. You wouldn't have had an accident if you had looked where you were going.
4. If it rains all night, the road'll be flooded by dawn.
5. He would come if you bothered to invite him.
6. If it hadn't been for the rain, we would have won the match.

In this list, there are two examples of each of the three basic types.  Divide up the list and think about what the sentences mean before you click for some comments.

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	First conditional
		If you push hard, it will move

The form of the first conditional is:

If	present tense	will	infinitive	or	will	infinitive	if	present tense
If	you come	you will	see		You will	see	if	you come

The form is easy enough and most learners get it quickly.  It is analogous to lots of other similar forms in English such as
    I will tell him when I see him.
    I will ask her to marry me because I love her.
The concept is slightly more difficult.  First conditional forms are concerned with future events and imply that if one condition is met (coming, pushing hard) the other event (seeing, moving) will follow.
    If it rains, I'll take an umbrella.
    If it doesn't snow again, I'll take the dogs out.
    What will you do if it rains?

We can use other modal auxiliary verbs to make the outcome less certain but the consequences of one action being followed by the other are still clear.  For example,
    If you come, you might see John.
    If you come, you should see John.
    If it stops snowing, I may take the dogs out.
    If he comes at all, he should be here by six.

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	Second conditional
		If I flew to the moon, I would look back and wave

The form of the second conditional is:

If	past tense	would	infinitive	or	would	infinitive	if	past tense
If	you came	you would	see		You would	see	if	you came

Again, this is not too complicated but there are two possible concepts here.

1. Unlikely condition: the speaker does not believe there is a high likelihood of an event occurring but if it does, the follow-on event is certain:
       If I won the lottery I'd be happy (but I don't think I'll win it).
       If they gave me an extra holiday, I would be really happy (but I don't think they will).
       What would you do if you won the lottery? (but I don't think you'll win)
2. Unreal condition: the speaker does not believe that an event is at all possible logically but is happy to speculate about the outcomes of an unreal event.
       If I were you, I'd buy it
       If I had a penny for every time I've said that, I'd be a wealthy woman.

Both unlikely and unreal conditionals are called hypothetical conditionals in many analyses.
Again, we can use other (past) modal auxiliary verbs to make the outcome less certain but the consequences of one action being followed by the other are still clear.  For example:
    If you came, you might see her.
    If you came, you could see her.
    If you went to the meeting you would have to explain the problem (so don't go).

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	Third conditional
		If you had been more careful, it wouldn't have broken

The form of the third conditional is:

If	past perfect tense	would have	past participle	or	would have	past participle	if	past perfect tense
If	you had come	you would have	seen		You would have	seen	if	you had come

Now that is complicated and learners need lots of practice just to get the form right.
This form refers only to the past and, therefore, in part to clearly unreal, impossible events.  It is used for regrets, criticisms and speculation and a number of other meanings.  Here are some examples:

regret

    If I'd had the money, I would have bought it
and I regret the fact that I didn't have the money.

criticism

    If you had driven more carefully, you wouldn't have dented the car
and I am suggesting that you should have driven more carefully.

speculation

    If Napoleon had won the battle of Waterloo, what would Europe have been like?
and I'm asking you to speculate about an impossible past situation.

Again, we can use other modal auxiliary verbs to alter the sense slightly.  For example:
    If you had driven more carefully, you might not have dented the car
in which I may simply be speculating about the past rather than criticising.
    If I'd had the money, I could have bought it
in which I am expressing past inability rather than regret.

Click for a quick test to see if you have grasped this.  It's important.

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Other issues

The so-called zero conditional

A form such as
    If you mix black and white you get grey
with a present tense in both halves and no will is sometime called a zero conditional.  There's an argument that it isn't a conditional at all because if can be replaced with whenever or when.  It is quite an easy form to learn and paralleled in some languages but some languages reserve a special word for if which is not interchangeable with whenever like this.

Speaker / writer perception

In particular when choosing between a 1st conditional and 2nd conditional form, it is the speaker's perception which matters most.  Compare:
    If I win the lottery, I'll buy a new house with
    If I won the lottery, I'd buy a new house
In the first, the speaker appears more optimistic than in the second.  The second is an unreal condition because the speaker does not believe it will happen.

Mixed conditionals

When there is a time change from one half of the conditional to the other, the tenses no longer seem to make sense sometimes.
There are two important forms of these sorts of mixed conditionals and they both mix second and third conditional structures:

1. a past action with a present consequence.  For example:
       If I had brought my car I would give you a lift
   Here, the beginning
       If I had brought
   usually implies an end of
       would have given
   but in this case the fact that I didn't bring the car is in the past but the consequence of not being able to give a lift lies either now or in the future so the tenses shift to allow this.
   Another example is:
       If she had told me where it was I wouldn't be wasting time looking
   in which a past non-event has a present consequence.
2. a present fact with a past consequence.  For example:
       If I weren't so busy this week, I would have taken the time to visit you
   in which the present state of being busy has an implication for an unrealized past act.
   Another example is:
       I would have finished by now if the boss didn't continually interrupt
   in which the present event affects the past.

Modal verbs in conditional sentences

We can use other modal verbs instead of will or would to change the sense of a conditional.  For example, we can change:
    If I go to the meeting, I will complain about it
to
    If I go to the meeting, I might complain about it
This can happen in all the conditional types so we can get sentences such as:
    If you had spoken more softly, she might have been more receptive
    If I won the money I could buy the car
and so on.

Other varieties of English

In colloquial American English (and other standards) it is common to have a sentence like
    If I would have known I would have said
or
    I would tell you if I would know
and there's a famous song with the line
    "If I knew you were coming, I'd have baked a cake".

The meaning of will

Compare:
    If you will give up smoking, I will stop complaining
and
    If you give up smoking, I will stop complaining.
In the first of these (If you will give up smoking), the word will means show willingness and is not a future form at all so the word appears in both parts of the sentence.  It could be re-phrased as
    If you commit to giving up smoking, I will commit to not complaining.
The second example is the familiar 1st conditional form in which the second event is dependent on the first.

Alternatives to if

A number of phrases can take the place of if and they change the style (usually making it more formal) but not the fundamental sense of the sentence.  For example:
    She'll come providing you invite her
    They'd pay as long as they had the money
    I'll do it on condition that you won't complain later

unless

This word is often understood to mean if not (i.e., it's the negative of if).  That's not exactly right because it really means only if ... not.
    Unless you have a car with you, I'll give you a lift home
    I'll open the box unless you tell me not to

Reversing the clauses

We can, of course, have
    If you came, you'd be able to talk to her
and
    You'd be able to talk to her if you came
They mean fundamentally the same thing but the emphasis is slightly different.  Speakers will generally put first what they consider most important.

There's a lot more to this area which hasn't been covered here but for most students, at most levels, that enough.

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Related guidestd>
condition and concession	for a more advanced guide to the area
conjunctions	an essential guide only with links to the more technical ones
modal auxiliary verbs	for a guide to the meanings of these special forms of verbs

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