Zero Conditional

The easiest conditional to understand is the zero conditional. We use this type of conditional when the condition put forward is an absolute. Indisputable scientific facts are often expressed as zero conditionals. For example, boil some water and see the vapor rise. This is a zero conditional.

IF	Condition	Result
	present simple	present simple
If	you boil water	vapor rises.

This is different than the other conditionals since the outcome is not questionable. The vapor rises; end of story. We are not concerned about past or future, we are referring to facts and conditions that always hold true.

IF	Condition	Result
	present simple	present simple
If	I run too fast	my knees hurt.
If	you whisper	I can’t hear.
If	you stay quiet	I can hear the water.
If	the door closes	I won’t get on the plane.

You can change the order of the clauses as seen below:

Result	IF	Condition
present simple	if	present simple
My knees hurt	if	I run too fast.
I can’t hear	if	you whisper.
I can hear the water	if	you stay quiet.
I won’t get on the plane	if	the door closes.