[ adjective, verb kuhm-pleks, kom-pleks; noun kom-pleks ]
See synonyms for: complexcomplexes on

  1. composed of many interconnected parts; compound; composite: a complex highway system.

  2. characterized by a very complicated or involved arrangement of parts, units, etc.: complex machinery.

  1. so complicated or intricate as to be hard to understand or deal with: a complex problem.

  2. Grammar.

    • (of a word) consisting of two parts, at least one of which is a bound form, as childish, which consists of the word child and the bound form -ish.

  3. Mathematics. pertaining to or using complex numbers: complex methods; complex vector space.

  1. an intricate or complicated association or assemblage of related things, parts, units, etc.: the entire complex of our educational system; an apartment complex.

  2. Psychology. a system of interrelated, emotion-charged ideas, feelings, memories, and impulses that is usually repressed and that gives rise to abnormal or pathological behavior.

  1. a fixed idea; an obsessive notion.

  2. Mathematics.

    • an arbitrary set of elements of a group.

    • a collection of simplexes having specified properties.

  3. Also called coordination compound. Chemistry. a compound in which independently existing molecules or ions of a nonmetal (complexing agent ) form coordinate bonds with a metal atom or ion.: Compare ligand (def. 2).

  4. Biochemistry. an entity composed of molecules in which the constituents maintain much of their chemical identity: receptor-hormone complex, enzyme-substrate complex.

verb (used with object)
  1. Chemistry. to form a complex with.

verb (used without object)
  1. Chemistry. to form a complex.

Origin of complex

First recorded in 1645–55; 1905–10 for def. 7; adjective from Latin complexus, past participle of complectī, complectere “to embrace, encompass, include,” equivalent to complect- (see complect) + -tus past participle suffix; noun from Late Latin complexus “totality, complex” (Latin: “inclusion, grasping, embrace”), equivalent to complect(ere) + -tus suffix of verb action; reanalysis of the Latin verb as “to intertwine (completely)” influenced sense of the adjective

Other words for complex

Opposites for complex

Other words from complex

  • com·plex·ly, adverb
  • com·plex·ness, noun
  • o·ver·com·plex, adjective
  • qua·si-com·plex, adjective
  • qua·si-com·plex·ly, adverb
  • su·per·com·plex, adjective
  • un·com·plex, adjective
  • un·com·plex·ly, adverb
  • un·com·plex·ness, noun

Words Nearby complex Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use complex in a sentence

British Dictionary definitions for complex


/ (ˈkɒmplɛks) /

  1. made up of various interconnected parts; composite

  2. (of thoughts, writing, etc) intricate or involved

  1. grammar

    • (of a word) containing at least one bound form

    • (of a noun phrase) containing both a lexical noun and an embedded clause, as for example the italicized parts of the following sentence: I didn't know the man who served me

    • (of a sentence) formed by subordination of one clause to another

  2. maths of or involving one or more complex numbers

  1. a whole made up of interconnected or related parts: a building complex

  2. psychoanal a group of emotional ideas or impulses that have been banished from the conscious mind but that continue to influence a person's behaviour

  1. informal an obsession or excessive fear: he's got a complex about cats

  2. Also called: coordination compound a chemical compound in which molecules, groups, or ions are attached to a central metal atom, esp a transition metal atom, by coordinate bonds

  3. any chemical compound in which one molecule is linked to another by a coordinate bond

Origin of complex

C17: from Latin complexus, from complectī to entwine, from com- together + plectere to braid

usage For complex

Complex is sometimes wrongly used where complicated is meant. Complex is properly used to say only that something consists of several parts. It should not be used to say that, because something consists of many parts, it is difficult to understand or analyse

Derived forms of complex

  • complexly, adverb
  • complexness, noun

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012