Linguistic Features of Formal and Informal Letter Writing in Modern English Summary Letter writing is an important communication skill in both personal and professional settings. There are different types of letters, including informal letters to friends and family, and formal letters used in business and academic spheres. The article deals with understanding that the differences between informal and formal letters, the appropriate tone, language, and format are essential for effective letter writing. Formal and informal language serve different purposes. It`s important to know when formal or informal writing is expected as it helps a writer to connect with the reader or listener. Formal and informal English are two distinct styles of language usage that vary in their level of formality, vocabulary, sentence structure and tone. Key words: writing skills, formal letters, informal letters, abbrevations, jargons, audience