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 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 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 group of two or more associated polypeptide chains Species complex, 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 polytope, a generalization of a polytope in a complex Hilbert space Complex analysis, the study of functions of complex 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 Building complex, a group of inter-related buildings Housing complex, specifically residential UCL Centre for Mathematics and Physics in the Life Sciences and Experimental Biology (CoMPLEX), part of UCL Faculty of Mathematical and Physical Sciences, London, UK See also Complexity (disambiguation) Complexity theory (disambiguation) Military–industrial complex