The zero conditional is used to talk about facts or things that are generally true. There are two types of facts: facts that are true for everyone, and facts that are true for a specific group. The zero conditional uses two present simple verbs - one in the 'if clause' and one in the 'main clause'. 'If' can usually be replaced with 'when' without changing the meaning. Several examples are provided to illustrate zero conditional structures. An exercise follows with blanks to fill in using the appropriate present simple verb forms.