An eBook (short for electronic book, also written eBook or e-book) is converted digital text that forms the equivalent of a conventional printed book, sometimes protected with a digital rights management (DRM*) system. The Oxford Dictionary of English defines the eBook as "an electronic version of a printed book," but eBooks can and do exist without any printed equivalent.
*DRM or Digital Rights Management refers to the controlled use of digital media by preventing access, copying or conversion to other formats by the end user.