From a working library:
The first definition is the most familiar: one who reads, or one who is fond of reading. A young girl tucked under a tree with a book in hand; an old man waiting for the bus, nose pressed into the spine; three little boys sitting on the curb sharing a newspaper, ink smudged on their knees.
The second definition harks back to the single-room schoolhouse: an anthology of texts used for teaching. Here the term passes from the person doing the reading to the object being read, from reading for its own sake to reading with intent. The image of reading remains, but it becomes focused, purposeful; it becomes work.
The third definition shifts from the object to the machine: a device for reading data. No longer human, the reader becomes mechanical, the texts reduced to ones and zeros. There are no stories, only limitless information, each digit as insignificant as the next.