The zero conditional is used to talk about
general truths,
or things that are almost always true
under certain conditions.
For example
it's pretty much always true that if it rains, stuff gets wet
Zero conditional is easy to form
because all the verbs are in present tense
You just use two clauses, one with
If + simple present verb
and the other with another simple present verb as in
"If students miss an exam, the professor fails them."
Or you can reverse the order of the clauses
You can say
"The professor fails students if they miss an exam."
Finally
this form can also be used for
giving instructions about what to do
under certain conditions
For example
"If I'm late for dinner, start eating without me."
Best regards
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