complex

Etymology

From French complexe, from Latin complexus, past participle of complector (“I entwine, encircle, compass, infold”), from com- (“together”) and plectere (“to weave, braid”). May be analyzed as com- + -plex. See complect. Doublet of complexus.

adj

1. Made up of multiple parts; composite; not simple.
   a complex being; a complex idea
2. Not simple, easy, or straightforward; complicated.
3. (mathematics, of a number) Having the form a + bi, where a and b are real numbers and i is (by definition) the imaginary square root of −1.
   complex number
   function of a complex variable
4. (mathematics, mathematical analysis, of a function) Whose range is a subset of the complex numbers.
   complex function
5. (mathematics, algebra) Whose coefficients are complex numbers; defined over the field of complex numbers.
   complex polynomial
   complex algebraic variety
6. (geometry) A curve, polygon or other figure that crosses or intersects itself.

noun

1. A problem.
2. A network of interconnected systems.
   military-industrial complex
3. A collection of buildings with a common purpose, such as a university or military base.
   The south polar region of Promethei Planum developed a Bermuda Triangle reputation. Satellites detected intermittent mass concentrations and magnetic field shifts. In 2148, prospectors working near Deseado Crater discovered an underground complex: a Prothean observation post. The odd phenomena were generated by the operation and discharge of a mass effect core, struggling to function despite fifty millennia of neglect. 2008, BioWare, Mass Effect (Science Fiction), Redwood City: Electronic Arts, →OCLC, PC, scene: Protheans: Mars Ruins Codex entry
   A man at the complex said he had seen the often heavily made-up girls coming and going in luxury vehicles. 6 Feb 2021, The Courier-Mail, Brisbane, page 4, column 1
4. An assemblage of related things; a collection.
   1. An organized cluster of thunderstorms.
   2. A cluster of wildfires burning in the same vicinity.
      The fire complex began as two separate fires.
      As of early Wednesday, there were at least 25 major wildfires and fire complexes, the term given to multiple fires in a single geographic area, burning in California, Christine McMorrow, a Cal Fire information officer, said. September 16, 2020, “Millions of acres burn in California as weather improves in Northwest.”, in The New York Times, retrieved 2020-09-16
   3. (taxonomy) A group of closely related species, often distinguished only with difficulty by traditional morphological methods.
      Since then, a good deal of research has documented and concluded that the nominal species A. fraterculus actually comprises an unresolved complex of cryptic species. November 26, 2015, Mosè Manni et al., “Relevant genetic differentiation among Brazilian populations of Anastrepha fraterculus (Diptera, Tephritidae)”, in ZooKeys, volume 540, →DOI
5. (psychoanalysis) An abnormal mental condition caused by repressed emotions.
6. (informal, by extension) A vehement, often excessive psychological dislike or fear of a particular thing.
   Jim has a real complex about working for a woman boss.
7. (chemistry) A structure consisting of a central atom or molecule weakly connected to surrounding atoms or molecules, as for example coordination complexes in inorganic chemistry and protein complexes in biochemistry.
   Oxygen levels on Earth skyrocketed 2.4 billion years ago, when cyanobacteria evolved photosynthesis:[…]. The evolutionary precursor of photosynthesis is still under debate, and a new study sheds light. The critical component of the photosynthetic system is the “water-oxidizing complex”, made up of manganese atoms and a calcium atom. 2013 September-October, Katie L. Burke, “In the News”, in American Scientist
8. (mathematics) A complex number.
   The interesting aspect here is that U₃ is irreducible, even though all irreps over the complexes are one-dimensional because ℤ₄ is abelian. 1996, Barry Simon, Representations of Finite and Compact Groups, page 50
9. (linguistics) A multimorphemic word, one with several parts, one with affixes.

verb

1. (chemistry, intransitive) To form a complex with another substance
2. (transitive) To complicate.