II. Conditional Mood

English conditional sentences can be divided into the two broad classes of factual/predictive and hypothetical (counterfactual), depending on the form of the verb in the condition (protasis).

In factual/predictive constructions the condition clause expresses a condition the truth of which is unverified. The verb in the condition clause is in the past tense (with a past tense interpretation) or in the present tense (with a present or future tense interpretation). The result clause can be in the past, present, or future. Generally, conditional sentences of this group are divided in two groups, the "zero conditional" and the potential or indicative conditional, often called "first conditional" or "conditional 1". This class includes universal statements (both clauses in the present, or both clauses in the past) and predictions [19].

1. Zero Conditional

The "zero" conditional is formed with both clauses in the present tense [12; 81]. This construction is similar across many languages. It is used to express a certainty, a universal statement, a law of science, etc.:

If you heat water to 100 degrees Celsius, it boils.

If you don't eat for a long time, you become hungry.

If the sea is stormy, the waves are high.

It is risky to eat prawns if they haven’t been kept at the right temperature.

We can use modal verbs in either clause, especially can and may [10; 121]:

Prawns can be risky to it if…

We use the zero conditional to talk about events or situations that can occur at any time, and often occur more than once, and their results:

If I eat oranges, I get red spots all over my skin.

We can use an imperative instead of a present tense in the result clause to give a general instruction [10; 121]:

If a chip pan sets alight, throw a fire blanket on it.

2. First Conditional

The potential or indicative conditional, often referred to as the "first conditional" or "conditional 1", is used more generally to express a hypothetical condition that is potentially true, but not yet verified. The conditional clause is in the present or past tense and the result can be in the past, present, or future [19].

Basic forms of Type 1 Conditionals [6; 282]:

'if-clause: main clause:

present tenses 'shall/will' future

condition to be satisfied likely outcome

be: If I am better tomorrow, I will get up.

have. If I have a headache I will take an aspirin.

simple present: If she finishes early she will go home.

present progressive: if he is standing in the rain, he will catch cold.

present perfect: If she has arrived at the station, she will be here soon.

present perfect progressive If he has been travelling all night, he will need a rest.

can, must. If I can afford it, I will buy it.

Some examples with the condition clause in the past tense:

If she took that flight yesterday, she arrived at 10pm.

If she took that flight yesterday, she is somewhere in town today.

If she took that flight yesterday, we'll see her tomorrow.

A condition clause in the present tense refers to a future event, a current event which may be true or untrue, or an event which could be verified in the future. The result can be in the past, present, or future:

If it's raining here now, then it was raining on the West Coast this morning.

If it's raining now, then your laundry is getting wet.

If it's raining now, there will be mushrooms to pick next week.

If it rains this afternoon, then yesterday's weather forecast was wrong.

If it rains this afternoon, your garden party is doomed.

If it rains this afternoon, everybody will stay home.

If I become President, I'll lower taxes.

Certain modal auxiliary verbs (mainly will, may, might, and could) are not usually used in the condition clause in English:

If it will rain this afternoon, …

If it may have rained yesterday, …

There are exceptions, however, in which will is used exactly as in the first example, namely when the action in the if -clause takes place after that in the main clause [13; 249]:

The weather forecast says it's going to rain. Well, if it will rain, we must take umbrellas. If aspirins will cure it, I'll take a couple tonight instead of this horrible medicine.

Other situations in which will can be used in an if- clause include when will is not being used as an auxiliary verb, in other words when it is being used modally to express willingness, persistence, refusal [10; 121] or a request [12; 84]:

If you'll just hold the door open for me a moment, I can take this table out to the kitchen. If you will keep all the windows shut, of course you'll get headaches. If you will excuse me, I think I will slip into something more comfortable.

If you want to make the request more polite you can use if … would:

If you would take your seats, ladies and gentlemen…

We may also use modal verbs in the main clause [6; 283]:

can (we are free to)

could (we would be able to)

may (it's possible)

If it's fine tomorrow, we might (it's possible) go out.

should (it's advisable)

ought to (it's advisable)

must (it's necessary)

Progressive and perfect combinations with modals are possible:

If I hear from Tim, I may be leaving tonight. If he is in New York he may not have got my letter yet.