Learn English Free and Fast - Zero Conditional

Zero

0 Conditional / Zero Conditional

Used to express general truths and facts (often things based on scientific fact).

Uses the simple present tense:-

(IF Clause)	(Main Clause)
If you heat water to 100°C,	it boils.

or...

(Main Clause)	(IF Clause)
Water boils	if you heat it to 100°C,

For example:

If you drop an apple, it falls. = An apple falls, if you drop it. (This is an absolute truth based on scientific fact - gravity).
If you don't do your homework, I will be disappointed. = I will be disappointed, if you don't do your homework. (This is a general truth based on previous knowledge - you know that I am disappointed if people don't do their homework).

Most zero conditional sentences mean the same thing if "when" is used instead of "if".