If conditions

First conditional[edit]
"First conditional" or "conditional I" refers to a pattern used in predictive conditional sentences, i.e. those that concern consequences of a probable future event (see Types of conditional sentence). In the basic first conditional pattern, the condition is expressed using the present tense (having future meaning in this context. In some common fixed expressions or in old-fashioned or formal The present subjunctive is occasionally found. For example:If need be, we'll rent a car. see use of the present subjunctive), and the consequence using the future construction with will (or shall):
If you make a mistake, someone will let you know.
If he asks me, I will/shall consider his proposal carefully.
The use of present tense in dependent clauses with future time reference is not confined to condition clauses; it also occurs in various temporal and relative clauses (as soon as he arrives; take the first train that comes; etc.), as described under Uses of English verb forms § Dependent clauses.
The present tense used in the condition clause may take the form of the simple present as in the above examples, or the present progressive, present perfect or present perfect progressive as appropriate (according to general principles for uses of English verb forms):
If he is sleeping when we arrive, we shan't wake him. (present progressive)
Will you wake him if he hasn't stirred by 10 o'clock? (present perfect)
If you have been working for more than ten hours when he returns, he will take your place. (present perfect progressive)
The condition can also be expressed using the modal verb should. This form can be used to make an inverted condition clause without a conjunction:
If you should make a mistake, ... (equivalent to "If you make a mistake")
Should you make a mistake, ... (inverted form equivalent to the above).
If you should be young, ... (equivalent to "If you are young")
Should you be young, ... (inverted form equivalent to the above)
Otherwise, the condition clause in a first conditional pattern is not normally formed with a modal verb, other than can. However, there are certain situations (often involving polite expressions) where will, would and could may be used in such clauses; see § Use of will and would in condition clauses below. For the occasional use of the subjunctive in the condition clause, see under zero conditional above. In colloquial English, an imperative may be used with the meaning of a condition clause, as in "go eastwards a mile and you'll see it" (meaning "if you go eastwards a mile, you will see it").
Although the consequence in first conditional sentences is usually expressed using the will (or shall) future (usually the simple future, though future progressive, future perfect and future perfect progressive are used as appropriate), other variations are also possible – it may take the form of an imperative, it may use another modal verb that can have future meaning, or it may be expressed as a deduction about present or past time (consequent on a possible future event):
If it rains this afternoon, come round to my place! (imperative)
If it rains this afternoon, we can/could/should/may/might find somewhere to shelter. (other modals)
If it rains this afternoon, then yesterday's weather forecast was wrong. (deduction about the past)
If it rains this afternoon, your garden party is doomed. (deduction placed in the present)
A particular case involves a condition clause that expresses a goal (this is often done using the be + to construction, the going-to future or the verb want), and the main clause expresses something that is necessary for the achievement of that goal, usually using a modal verb of necessity or obligation. In this case it is effectively the main clause, rather than the dependent condition clause, that expresses a "condition".
If we want to succeed, we have to try harder.
If you are to get your pocket money, you must start behaving yourself.
As noted in the following section, it may be possible to express a statement about a hypothetical future situation using either the first or second conditional pattern, with little specific difference in meaning.