Java package | subsystem | if related aspects of a system are kept together in this module, and unrelated aspects are kept out | a name space | A collection of classes and interfaces | to group together related classes into a subsystem | reusable if it can be used in several different systems with little or no modification | package^3 | Java package name | The Basics of Java | side effects if it does not modify any data, and does not leave behind any information, other than its result, that would have an effect on other computations | package^2 | a special-purpose function such as the user interface for a particular system | using the import statement |