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Concourse 2

Conditionals: the essentials

if
From "If" by Rudyard Kipling

A conditional sentence is defined on this site as:

A sentence which consists of two clauses at least, one of which expresses the condition (the protasis) and contains the conditional conjunction or other marker of condition and one which expresses the consequence of the fulfilment of the condition (the apodosis).
(From the glossary of grammar, lexis and phonology)

For example, in the sentence:
    If you come to the party, you'll be able to meet his sister
there are two clauses:

  1. The protasis:
        If you come to the party
    which expresses the condition
  2. The apodosis
        you'll be able to meet his sister
    which expresses the consequence of coming to the party.

Another way of putting this is to state that 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.

1st

First conditional

 push
If you push hard, it will move

The form of the first conditional is:

Conditional clause Main clause or Main clause Conditional clause
If present tense will infinitive 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 replace will and make the outcome less certain, advisory or obligatory 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
    If you want a pay rise, you must speak to the boss
    If you have a headache, you should go and lie down

2nd

Second conditional

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

The form of the second conditional is:

Conditional clause Main clause or Main clause Conditional clause
If past tense would infinitive 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.
It is quite arguable that the use of the term unreal to describe all second conditional forms is misleading.  Some are unreal in the sense that they can never logically occur but others are simply an expression of unlikelihood and could become real.
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)

ambiguity with modal auxiliary verbs

The use of might always expresses a less certain outcome, because the verb refers to likelihood alone.
The use of could is ambiguous, because it can refer to likelihood but may also refer to ability (in its guise as the past form of can).  This means that a sentence such as:
    If you arrived late you could miss the opening speeches
is interpretable two ways:

  1. If you arrived late you would be in danger of missing the opening speeches
    (an undesirable outcome)
  2. If you arrived late you would be able to miss the opening speeches
    (a desirable outcome)
3rd

Third conditional

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

The form of the third conditional is:

Conditional clause Main clause or Main clause Conditional clause
If past perfect tense would have past participle 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, applies 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.

The same ambiguity with the use of the modal auxiliary verb could applies here as it is explained above.  For example, the sentence:
    If she had taken the train, she could have left her car at John's place
can mean either:
    If she had taken the train, it is conceivable that she left her car at John's place
or
    If she had taken the train, she would have been permitted to leave her car at John's place
and only the context can tell us what is meant.

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

issues

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 parallelled in some languages.  However, some languages reserve a special word for if which is not interchangeable with whenever like this.
The form of zero conditionals is also present in expressions such as:
    I'm happy if you are
but in that the speaker is probably already sure that the hearer is happy so no real conditional sense is implied.
First conditional imperatives
By their nature imperative sentences refer to the future so it is often the case that a future form in a first conditional is not required (and is often wrong) so we can have, for example:
    If you need help, please ask
    If you have time, come for a drink
First conditionals and the present perfect
Because the present perfect is a present tense (it simply embeds the past in the present), it appears in many first-conditional sentences so we get, e.g.:
    I'll wash that up if you have finished with it
    If she has arrived, I'll start the meeting
and so on.
Speaker / writer perception
In particular when choosing between a 1st conditional and 2nd conditional form, it is the speaker's perception which matters most.  Both forms refer to the future and the question is how likely the speaker or writer sees the future event.  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 (better hypothetical) conditional 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 (although the more complex guide in the in-service section, linked below, discusses four others) 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 unrealised 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 auxiliary verbs in conditional sentences
We can use other modal auxiliary 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
    If you want her to help you should be more polite to her
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
It is usually said that having two instances of will in a conditional sentence is wrong so, for example, it is in:
    *If I will win I will be happy
However, will has two meanings and this is not always clear.
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 will appears in both parts of the sentence.  It could be rephrased as
    If you commit to giving up smoking, I will commit to not complaining
The second example is the familiar first conditional form in which the second event is dependent on the first and the verb will refers to futurity, not willingness, so will only appears once.
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
    But me a drink and I'll give you a lift home
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.
Conditional without conjunctions
We can make conditional sentences in English without using if or any alternative conjunctions.  Here are some examples:
    Should you need any help, just ask
    Had you been at the meeting you would know the procedure
    Were you to come to the party, you'd meet his new wife
Altering the word order like this often means that the sentence is stylistically much more formal.
Half a conditional
In spoken discourse, turn-taking by completing or responding to what you have heard is common.  We get therefore, exchanges like this:
    A: Will you take the car tomorrow?
    B: If it's raining
    A: That's the wrong word
    B: Oh, what would you call it?
    A: I'll eat at the hotel
    B: Oh, I would have cooked you lunch here
and it's clear that a good speaker of the language can fill in the missing halves of the conditional sentences as:
    If it's raining I'll take the car
    What would you call if you were asked?
    I would have cooked you lunch here if you weren't eating at the hotel
but it is much more difficult for a learner to do that, especially in the third case because we have a mixed conditional sentence.
Pronunciation
There are a number of pronunciation issues.
The most important is that learners may not even hear that a sentence is conditional at all because fluent speakers often reduce the word if to a barely recognisable /f/ sound spoken very indistinctly.
Other issues concern the pronunciation of combinations of a verbs in, for example:
    If you hadn't been so rude to her she wouldn't've been upset
in which normally only rude and upset are given any stress and the rest of the sentence is indistinctly pronounced.
For more on the pronunciation issues see the in-service guide, linked below.

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


Related guides
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 types of verbs