(1) In communication, a technique used by layered protocols by which a layer adds control information to the protocol data unit (PDU) from the layer it supports. In this respect, the layer encapsulates the data from the supported layer. In the Internet suite of protocols, for example, a packet would contain control information from the physical layer, followed by control information from the network layer, followed by the application protocol data. See also decapsulation.
(2) In object-oriented programming, the technique that is used to hide the inherent details of an object, function, or class from client programs.