The state of being complex; intricacy; entanglement.

That which is complex; intricacy; complication.

Unnecessary work; any activity that makes a work process more complicated without adding value to the resulting product or service.

While, chaos is the study of how simple systems can generate complicated behavior, complexity is the study of how complicated systems can generate simple behavior. An example of complexity is the synchronization of biological systems ranging from fireflies to neurons. (From the FAQ sheet of the sci.nonlinear newsgroup).

It's a nonlinear, interconnected world and you will never figure it out. Shit happens.

The level of intricacy in the logic of the solution or problem or the degree of difficulty and amount of time to implement a particular design or piece of software.

The interaction of many parts, giving rise to difficulties in linear or reductionist analysis due to the nonlinearity of the inherent circular causation and feedback effects.

Closely related to variety, a principle of design, this term refers to a way of combining the elements of art in involved ways, to create intricate and complicated relationships. A picture composed of many shapes of different colors, sizes, and textures would be called complex.

The degree of complication of a system or system component, determined by such factors as the number and intricacy of interfaces, the number and intricacy of conditional branches, the degree of nesting, the types of data structures, and other system characteristics.

Complexity has two primary forms: complexity of component detail and complexity out of fluctuation over time. Component complexity is complicated, intricate and involved. By the iteration of feedback over time the complex system becomes chaotic.

Complexity in general usage is the opposite of simplicity. Complexity in specific usage is the opposite of independent while complicated is the opposite of simplicity.