If I was writing this article just five years ago, when asked what an ebook is, I would probably have said a PDF. Where PDF is an acronym for Portable Document Format which, unlike say an Word document, is read-only and retains all the source formatting and layout.
Nowadays, with the increasing ubiquity of ereaders, it might be tempting to define an ebook as something you downloaded to be read on an Amazon Kindle or Apple iPad. To make matters slightly more confusing, the humble PDF can be read on both devices.
Where a PDF essentially differs from a book formatted for an ereader is that the latter, be it in ePub, HTML5 or the techie format, tends to be copy protected and tied to the purchaser’s account – not even their device. This means they can read it on their Kindle, iPhone and computer if they own all three.
Neither of these descriptions however fully defines what an ebook is or can be.