A complex number is a number of the form "a + bi", where a and b are real numbers and i is the imaginary number.

In general usage, complexity often tends to be used to characterize something with many parts in intricate arrangement. In science there are at this time a number of approaches to characterizing complexity, many of which are reflected in this article....

Complex (chemistry), also called a "coordination compound" or "metal complex", is a structure consisting of a central atom or molecule weakly connected to surrounding atoms or molecules.

A complex is an element of a complex algebra or field of sets.

A 'mimicry complex' is a group of organisms involved in mimicry, being made of one or more mimics, models and dupes.

A chain complex is a (possibly long) sequence of maps.

A simplicial complex is a kind of topological space that can be divided into fully adjacent triangles, or more generally, into simplices.

A CW complex, or closure-finite weak complex, is a kind of topological space, a generalization of the simplicial complex.

Complex (psychology), a group of mental factors that are unconsciously associated by the individual with a particular subject and influence the individual's attitude and behavior.

Complex (song), a 1979 song by Gary Numan

Complex (band), a Japanese rock duo

Complex (magazine)

A complex in the taxonomy of biology is a cluster of species so closely related that they intergrade, can interbreed, and are difficult to firmly distinguish except at the extremes of their ranges

An abbreviation for complex analysis, the study of functions of complex numbers.

A complex system is a system comprised of interconnected simple parts that together exhibit a high degree of computational complexity from which emerges a higher order behavior.