coupling

The phase state in which either two dominant or two recessive alleles of two different genes occur on the same chromosome. Synonym: cis configuration. Opposite: repulsion; trans configuration.

Coupling arises when classes are aware of each of other because their instances must interact. Linkage between two classes that may be either strong or weak. Stronger coupling arises when one class has a detailed knowledge of the internal implementation of another, and is written to take advantage of that knowledge. So anything that has the potential to reduce the amount of inside knowledge will tend to weaken coupling. Hence, information hiding and encapsulation. Java's visibility levels - private, package, protected, public - progressively reveal detail to other classes, and so increase the potential for stronger coupling. Interfaces are one way to reduce to reduce coupling - because you interact with a class via an abstract definition, rather than a concrete implementation.

The desirable or undesirable transfer of energy from one medium, such as a metallic wire or an optical fiber, to another like medium, including fortuitous transfer. Note: Examples of coupling include capacitive (electrostatic) coupling, inductive (magnetic) coupling, conducted (resistive or hard-wire) coupling, and fiber-optic coupling.