Complex commonly refers to: * Complexity, the behaviour of a system whose components interact in multiple ways so possible interactions are difficult to describe **

Complex system A complex system is a system composed of many components that may interact with one another. Examples of complex systems are Earth's global climate, organisms, the human brain, infrastructure such as power grid, transportation or communication sy ...

, a system composed of many components which may interact with each other * Complex (psychology), a core pattern of emotions etc. in the personal unconscious organized around a common theme such as power or status Complex may also refer to:

Arts, entertainment and media

* Complex (English band), formed in 1968, and their 1971 album ''Complex'' * Complex (band), a Japanese rock band * ''Complex'' (album), by Montaigne, 2019, and its title track * ''Complex'' (EP), by Rifle Sport, 1985 * "Complex" (song), by Gary Numan, 1979 * "Complex", a song by Katie Gregson-MacLeod, 2022 * "Complex" a song by Be'O and Zico, 2022 * Complex Networks, publisher of the now-only-online magazine ''Complex''

Biology

* Protein–ligand complex, a complex of a protein bound with a ligand * Exosome complex, a multi-protein intracellular complex *

Protein complex A protein complex or multiprotein complex is a group of two or more associated polypeptide chains. Protein complexes are distinct from multidomain enzymes, in which multiple active site, catalytic domains are found in a single polypeptide chain. ...

, a group of two or more associated polypeptide chains *

Species complex In biology, a species complex is a group of closely related organisms that are so similar in appearance and other features that the boundaries between them are often unclear. The taxa in the complex may be able to hybridize readily with each oth ...

, a cluster of very similar species difficult to delimit * Pre-Bötzinger complex, a cluster of interneurons in the ventral respiratory group of the medulla of the brainstem

Chemistry

* Coordination complex, a central atom or ion and a surrounding array of bound molecules or ions * Chelate complex, a coordination complex with more than one bond

Mathematics

* Complex number, an extension of real numbers obtained by adjoining imaginary numbers * Complex, an element of a field of sets * Chain complex, an algebraic structure * Simplicial complex, a kind of topological space * CW complex, a kind of topological space * Line complex, a 3-dimensional family of lines in space

Geology

* Complex (geology), a unit of rocks composed of rocks of two or three types * Complex crater, a type of large impact crater morphology * Volcanic complex, a group of volcanoes * Complex volcano, a volcano of mixed form * Accretionary complex, a fossil accretionary wedge

Other uses