Following definitions of writing, the chapter elaborates on writing as a language skill, and its relationship to speaking and reading. Next, writing as a tool for learning to write, and a tool for learning the language and the content are described. The subsequent section presents the potential difficulties writing poses to writers. Then, writing in a native language is compared to writing in a target language. As no discussion of writing can be complete without considering cultural influences on text production, one section is devoted to this topic. Later on, writing is addressed as an act of communication with a range of forms and functions that it can take and perform. Next, brief insights are given into the components of effectively written texts, and the clarity and readability of the written discourse. Finally, the domain of scientific writing, with a focus on plain language, is addressed.