In computer technology and telecommunications, online indicates a state of connectivity, and offline indicates a disconnected state, specifically an internet connection.
Online and offline are defined by Standard 1037C. They are states or conditions of a "device or equipment" or of a "functional unit". To be considered online, one of the following may apply to a system: it is under the direct control of another device; it is under the direct control of the system with which it is associated; or it is available for immediate use on demand by the system without human intervention.
In contrast, a device that is offline meets none of these criteria (e.g., its main power source is disconnected or turned off, or it is off-power).
The Oxford dictionary defines "online" (sometimes also referenced as "On the Line") as "controlled by or connected to a computer" and as an activity or service which is "available on or performed using the Internet or other computer network". The term is utilized within terms such as these: "online identity", "online predator", "online gambling", "online shopping", "online banking", and "online learning". The online context is given to other words by the prefixes "cyber" and "e", as in the words "cyberspace", "cybercrime", "email", and "ecommerce".