An electronic book (variously: e-book, eBook, e-Book, ebook, digital book or e-edition) is a book-publication in digital form, consisting of text, images, or both, readable on computers or other electronic devices. Although sometimes defined as "an electronic version of a printed book", many e-books exist without any printed equivalent. Commercially produced and sold e-books are usually intended to be read on dedicated e-readers. However, almost any sophisticated electronic device that features a controllable viewing screen, including computers, tablets and smartphones can also be used to read e-books.