First Conditional expresses a real possibility in future. The situation is possible to happen sometime in future.
Why do we use it?
We use it to talk about the possible present and future situations.
If it rains tomorrow, we won't go to the picnic.
If you exercise every day, you'll lose weight.
When we get home, I'll call you.
We can use 'when' instead of 'if' in first conditionals. 'When' expresses a statement that will happen sometime in future. We are sure that it will happen. However, 'if' expresses a real possibility. We are not sure, it may happen or not.
For example :
"If the train departs on time, we'll be in Dublin at two o'clock in the afternoon."
"When my daughter is eighteen years old, I'll buy her a car."
How do we form it?
We use the present simple in the first clause and future simple (will) in the second clause.
If you arrive on time, we'll go to my grandma's house.
Are there any other forms?
You can make many variations both in the “if clause” and “result clause”. The meaning changes according to the meaning of the variation.
Variations in Result Clause
There are different modal verbs used in the result clause instead of future simple tense (will).
- Possibility: may/might > If it doesn’t rain tomorrow, we may/might go to the picnic.
- Permission/offer: may/can > You can come with us If you want.
- Ability: can > If you study hard, you can pass your exams.
- Advice/Necessity/Order: must/have to/should or imperatives> If you want to buy a new car, you must/should save some money. (Must is stronger advice than should) If you want to be fit, go on a diet. (order)
Variations in Condition Clause
You can also use present continuous or present perfect tenses in the “if clause”.
If he’s writing the letter now, he’ll finish it on time. (Commenting on the present action)
If he’s made progress so far, he’ll be successful eventually. (Commenting on the action so far)
If you have finished your assignment, go and submit it today. The deadline is today. (Giving order upon the condition finished in indefinite past time)
What’s the difference between zero and first conditionals?
With zero conditionals we are talking about a general fact. So, when we want to express scientific facts, it’s best to use zero conditional. However, when we use first conditional, we are talking about a specific situation.
If you eat fast food every day, your health gets worse. (Here, we are talking about a natural consequence of eating fast food. This is something that happens to everybody who eats fast food every day.)
If you eat fast food, your health will get worse. (Here, we are talking to about possible result of eating fast food every day. The speaker is not stating this as a general fact. It’s just a possible consequence, it isn’t a scientific fact. There are other possible results for the situation.)