This document provides information about letters, including their definition, parts, common salutations, types, and expressions used. A letter is a written communication usually sent via mail or post to facilitate communication between individuals. Common salutations include "Dear Sir or Madam" for formal letters and greetings like "Hello" for informal letters. Letters can be for purposes like job applications, keeping in touch with relatives, thank you notes, or writing to friends. Key parts include the greeting, opening paragraph, main paragraphs, closing paragraph, and farewell expressions. The document also lists expressions commonly used for inviting, reminding, congratulating, apologizing, accepting, suggesting, arranging meetings, offering, refusing, explaining, asking questions, expressing preferences,