Conditionals are used to show the results when a certain action occurs. A conditional sentence requires two clauses - the protasis (the clause that expresses the condition) and the apodosis (the clause that expresses the consequences). Example: If you press that button, the light will shine. The protasis may be known to either be false or highly unlikely, where a special type of conditional called a counterfactual is needed. Example: If he were stupid, he would have failed the test. Example: If I turn into a zombie, I will eat you! Example: If/when water reaches 100 degrees, it evaporates.