Several prefixes are added to a wide range of existing words to describe new, Internet- or computer-related products and services that already have a non-electronic counterpart.
“e-”, standing for “electronic”, is used in terms like e-reader, e-mail, e-book, e-business, e-commerce, e-banking.
Several sources, such as the AP Stylebook and The Economist Style Guide, recommend hyphenating these words. However, email is now much more usual than e-mail. Except at the start of a sentence, the “e-” is lower case. Most computer terms are usually lower case: dotcom, home-page, laptop, online, the net, the web, website.
The hyphen may get lost over time, but for now it is commonly used. The choice between e-reader and ereader could be considered a style choice, but eReader* is wrong. Brand names sometimes use the so-called camel case (an internal capital letter), but in standard English such style is unacceptable for anything other than names.
“i-”, standing for “Internet”, has been used by some communities, services and brands since 1994. It is now often associated with a company which uses this prefix before most of its devices and products.
“cyber-” is derived from “cybernetic”, which comes from Greek and means “skilled in governing or steering”. It is used in terms such as cyberspace, cybercrime, cyberterrorism or cyberbullying.