com·​plex | \ ˈkäm-ˌpleks How to pronounce complex (audio) \

Definition of complex

 (Entry 1 of 3)

1 : a whole made up of complicated or interrelated parts a complex of welfare programs the military-industrial complex
2a : a group of culture traits relating to a single activity (such as hunting), process (such as use of flint), or culture unit
b(1) : a group of repressed desires and memories that exerts a dominating influence upon the personality a guilt complex
(2) : an exaggerated reaction to or preoccupation with a subject or situation He has always had a complex about spiders. She has a weight complex. Not being able to find a job was giving me a complex.
c : a group of obviously related units of which the degree and nature of the relationship is imperfectly known
d : the sum of factors (such as symptoms) characterizing a disease or condition primary tuberculous complex
3 : a chemical association of two or more species (such as ions or molecules) joined usually by weak electrostatic bonds rather than covalent bonds
4 : a building or group of buildings housing related units an apartment complex a sports complex


com·​plex | \ käm-ˈpleks How to pronounce complex (audio) , kəm-ˈpleks, ˈkäm-ˌpleks \

Definition of complex (Entry 2 of 3)

1a : composed of two or more parts : composite a complex mixture of chemicals
b(1) of a word : having a bound form as one or more of its immediate constituents Unmanly is a complex word.
(2) of a sentence : consisting of a main clause and one or more subordinate clauses
2 : hard to separate, analyze, or solve a complex problem
3 : of, concerned with, being, or containing complex numbers a complex root complex analysis


com·​plex | \ käm-ˈpleks How to pronounce complex (audio) , kəm-ˈpleks, ˈkäm-ˌpleks \
complexed; complexing; complexes

Definition of complex (Entry 3 of 3)

transitive verb

1 : to make complex or into a complex
2 : chelate

Other Words from complex


complexly adverb
complexness noun


complexation \ ˌkäm-​ˌplek-​ˈsā-​shən How to pronounce complex (audio) , kəm-​ \ noun

Choose the Right Synonym for complex


complex, complicated, intricate, involved, knotty mean having confusingly interrelated parts. complex suggests the unavoidable result of a necessary combining and does not imply a fault or failure. a complex recipe complicated applies to what offers great difficulty in understanding, solving, or explaining. complicated legal procedures intricate suggests such interlacing of parts as to make it nearly impossible to follow or grasp them separately. an intricate web of deceit involved implies extreme complication and often disorder. a rambling, involved explanation knotty suggests complication and entanglement that make solution or understanding improbable. knotty ethical questions

The Complex Origins of Complex

The word complex lives up to its name, as it contains multiple parts of speech and senses. It serves as an adjective, a noun, and, less commonly, as a verb. The verb use is the oldest of the three, with an original meaning of “to join or unite.” Complex comes from the Latin complecti, which means “to entwine around, to embrace,” a word that is based in part on plectere (“to braid”). English has a number of other words that can be traced to plectere, including perplex, plexus (“an intricately interwoven combination of elements or parts in a cohering structure”), and amplexus (“the mating embrace of some amphibians, such as frogs and toads”).

Examples of complex in a Sentence

Noun She has a complex about her appearance. a complex of protein molecules Adjective The house's wiring is complex. The situation is more complex than you realize. Verb there's no need to complex what should be a simple process for obtaining a building permit
Recent Examples on the Web: Noun The complex, which took more than seven years and 6,000 workers to build, operated for only eight years. New York Times, 22 May 2022 However, the weather service noted there is a chance a storm complex, or MCS, could develop in Mississippi and make it into parts of northwest Alabama later tonight before dissipating. Leigh Morgan, al, 21 May 2022 This undeniably cool cologne is warm and spicy thanks to its key notes of sage, triple black spice complex, and roasted almonds accented by bergamot, pink pepper, chili, cinnamon, smooth tobacco, aged leather, and sensual vetiver. Grooming Playbook, The Salt Lake Tribune, 20 May 2022 Aurora has approved final plans for a 246-unit, $70 million apartment complex on North Broadway in downtown. Steve Lord, Chicago Tribune, 20 May 2022 Officers chased him about two blocks and into an apartment complex, where he was taken into custody. Karen Kucher, San Diego Union-Tribune, 19 May 2022 With the help of Bob Divola from the city’s Department of Public Works and an employee from a nearby apartment complex, MacIntosh and Riordan were able to use a pool skimmer to extricate the ducklings from the drain. Emily Sweeney,, 18 May 2022 In addition to the Hartford 21 complex, which surrounds the XL Center and is across the street from 242 Trumbull, Northland also owns the vacant, former YMCA building in a prominent location across from Bushnell Park. Kenneth R. Gosselin, Hartford Courant, 17 May 2022 This complex of living history museums, which has indoor and outdoor elements, teaches visitors about the European settlement of Plymouth Colony and the history of the native Wampanoag people. Rachel Walker, Washington Post, 13 May 2022 Recent Examples on the Web: Adjective Gurman rightly points out that the situation is complex. David Phelan, Forbes, 13 May 2022 Russia’s struggles underscore how real wars are far more complex, said Stephen Biddle, a Columbia University professor who served on strategic assessment teams for U.S. generals David Petraeus and Stanley McChrystal in Iraq and Afghanistan. Josh Zumbrun, WSJ, 13 May 2022 Bob Fosse’s semi-autobiographical musical extravaganza opens with a flurry of high kicks and jazz hands, but what lies beneath its shiny surface is much more complex. Radhika Seth, Vogue, 12 May 2022 Some recipes are complex, like making wine from muscadine grapes, or stuffing shad with parsley rice and serving it with roe — a two-day effort. New York Times, 9 May 2022 There is also the fact that the production, which was delayed for about four months due to the COVID-19 pandemic, is rather technically complex. Brendan Morrow, The Week, 5 May 2022 But despite the increase in sales and activity, data from CarGurus reveals consumer buying habits are a little more complex. Nik Popli, Time, 3 May 2022 The Parkland case is more complex than the others and will take longer at each stage. Rafael Olmeda, Sun Sentinel, 3 May 2022 While many countries have a cutoff for abortions of 15 weeks or earlier, the differences around the world are complex, as The Washington Post previously reported. Washington Post, 3 May 2022 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'complex.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of complex


1643, in the meaning defined at sense 1


1645, in the meaning defined at sense 1a


1658, in the meaning defined at sense 1

History and Etymology for complex


Late Latin complexus totality, from Latin, embrace, from complecti — see complex entry 2


Latin complexus, past participle of complecti to embrace, comprise (a multitude of objects), from com- + plectere to braid — more at ply

Learn More About complex

Time Traveler for complex

Time Traveler

The first known use of complex was in 1643

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Dictionary Entries Near complex



complex carbohydrate

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Statistics for complex

Last Updated

28 May 2022

Cite this Entry

“Complex.” Dictionary, Merriam-Webster, Accessed 28 May. 2022.

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More Definitions for complex


com·​plex | \ käm-ˈpleks How to pronounce complex (audio) , kəm-ˈpleks, ˈkäm-ˌpleks \

Kids Definition of complex

1 : not easy to understand or explain : not simple complex instructions
2 : having parts that go together in complicated ways a complex invention


com·​plex | \ käm-ˈpleks How to pronounce complex (audio) , kəm-ˈ How to pronounce complex (audio) , ˈkäm-ˌ \

Medical Definition of complex

 (Entry 1 of 3)

1 : having many varied interrelated parts, patterns, or elements and consequently hard to understand complex behavior a complex personality complex plants and animals
2 : formed by the union of simpler chemical substances complex proteins


com·​plex | \ ˈkäm-ˌpleks How to pronounce complex (audio) \

Medical Definition of complex (Entry 2 of 3)

1 : a group of repressed memories, desires, and ideas that exert a dominant influence on the personality and behavior a guilt complex — see castration complex, electra complex, inferiority complex, oedipus complex, persecution complex, superiority complex
2 : a group of chromosomes arranged or behaving in a particular way — see gene complex
3 : a chemical association of two or more species (as ions or molecules) joined usually by weak electrostatic bonds rather than by covalent bonds
4 : the sum of the factors (as symptoms and lesions) characterizing a disease primary tuberculous complex


transitive verb
com·​plex | \ käm-ˈpleks How to pronounce complex (audio) , kəm-ˈ How to pronounce complex (audio) , ˈkäm-ˌ \

Medical Definition of complex (Entry 3 of 3)

1 : to form into a complex RNA complexed with protein
2 : chelate

intransitive verb

: to form a complex hormones which must complex with specific receptors

More from Merriam-Webster on complex

Nglish: Translation of complex for Spanish Speakers

Britannica English: Translation of complex for Arabic Speakers Encyclopedia article about complex


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