[STATEMENT] 1. Conditional sentences have two clauses: a condition (if...) and a result. 2. The verb tense used in each conditional depends on whether the speaker thinks the rooult is probabic (real) or only exists in the imagination (unreal). 3. The third conditional is a structure used for talking about general truths. 4. The zero conditional is used to talk about things which are unreal (not true or not possible). 5. If the "if" clause comes first, there's no need for a comma.