Behavior	The set of services that an entity provides.
Class	A template that specifies the structure and behavior of a set of objects.
Instance	A particular object having the structure and behavior specified by its class.
Instance variable	A data resource of a particular object.
Object	Synonym for instance.
Message	The means by which an object requests a service from another object.
Method	The operation performed by an object when it receives a message.
Receiver	An object that detects a request for a service.
Sender	An object that requests a service.