This document provides an overview of letter writing conventions in English. It discusses the purpose of learning letter writing and defines the main types of letters, including social correspondence letters (such as letters to friends, relatives, and colleagues), business correspondence letters, and the mechanics of writing letters. The document then examines the typical layout of letters, including the heading, personalized letterhead, inside address, salutation, body, complementary close, signature, and postscript. It also discusses the formats and appropriate wording for different types of social letters (invitations, replies, congratulations, condolences, thank you notes) and business letters (complaints, apologies, recommendations, applications, requests, resignations, resumes).