Zero Conditional in English Grammar
'If you don't eat or drink, you die'. 'If you heat water, it boils'. Zero conditional is used to talk about facts or situations which are always true.
Conditionals in grammar are sentences or clauses that begins with 'if' or 'unless' and express a condition.
Zero conditional is often used for something that is generally true and do not change, something that always happens if a condition is met, like a scientific fact. The condition always has the same result.
Water always boils when it is heated. It's a fact. That is a zero conditional sentence.
Zero Conditional: Structure
The basic structure of a zero type conditional is like this:
'If A, B' or,
'If + condition, result'.
A and B are usually in the present simple tense. The present simple describes facts. But, the result can also be in imperative mood.
This is an example of Type 0 conditionals. The condition always has the same result.
Here, the result is in imperative mood.
An if clause is the conditional clause that starts with 'if'. You have to use a comma (,) at the end of an 'if clause'. 'If clause' usually comes at the beginning of the sentence.
The part or clause after the comma (,) is called the result or the main clause.
'If you mix red paint and yellow paint' is our 'if clause'. Note that after the if clause we have a comma. 'you get orange paint' is the result.
Reversing A and B
You can reverse the order of A (if clause) and B (the main clause) and say the result first, then state the condition. Note that in this order, you do NOT use a comma between the clauses.
'You burn your hand' is the result and 'if you keep it above fire' is the if clause.
Instead of 'if', you can also use 'when' or 'unless'. 'Unless' means 'if not'. See the examples:
Unless something unexpected happens, we go to work tomorrow. Remember, if unless clause be the first clause we should have a comma before the result clause.
Unless is used to talk about a situation that could happen, or something that could be true, in the future. If you know that something has not happened or that something is not true, use 'if… not'.
We can often use 'when' instead of 'if'. It won't change the meaning of the sentence. We can use 'when' because the result always happens when the condition is true.
Zero Conditional in the Past
You can use zero conditionals in the past simple tense to talk about facts and situations that always happened in the past. It talks about facts and routines and habits that were always true in the past.