This document provides explanations and examples of regrets and conditionals in English grammar. It discusses using "should have" and "ought to have" to talk about past events that did not happen or may have happened. It also discusses the three types of conditionals - 1st conditional for present/future possibilities, 2nd conditional for imaginary situations, and 3rd conditional for impossible past situations. Finally, it notes that "if" can be replaced by linking words like "unless", "as long as", and "provided" to introduce conditional clauses.