a written document: anything committed to writing, from a letter to a legal deed to a book
At its core this word names something written down. In a world where most people could not read, putting words on a scroll gave them a fixed, portable, lasting form, and this single word covers the whole range of what writing was used for: a message sent across distance, a contract that settled who owned what, a sacred text read aloud to the nation, an official register of names. The shades below are not different words but different jobs the same written thing was doing.
What holds the senses together is permanence and authority. A spoken word fades, but a written one can be sealed, stored, carried, produced as evidence, and read again years later. So the word leans toward documents that bind: a king's order, a deed of sale, the covenant law, the record God himself keeps. Even the rarer sense of writing as a skill (Daniel and his companions learning the "writing" of the Babylonians) belongs here, because it is the ability to handle these written things.
The physical object varied, most often a rolled scroll, sometimes a single sealed sheet, but the word points to the content and its standing rather than the material. Where the focus is on the physical roll itself, Hebrew has a separate word for that.