Trivia Time

Which psychologist popularized the modern psychological concept of a complex?

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complex

American  

[kuhm-pleks, kom-pleks, kom-pleks] / kəmˈplɛks, ˈkɒm plɛks, ˈkɒm plɛks /

adjective

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.

   Antonyms:

   simple

3. so complicated or intricate as to be hard to understand or deal with.

   a complex problem.

   Synonyms:

   labyrinthine, tangled, knotty

   Antonyms:

   simple

4. Grammar.

   1. (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.

   2. complex sentence.

5. Mathematics. pertaining to or using complex numbers.

   complex methods; complex vector space.

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noun

• complexes
  plural

1. an intricate or complicated association or assemblage of related things, parts, units, etc..

   the entire complex of our educational system; an apartment complex.

   Synonyms:

   labyrinth, tangle, web, network

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.

3. a fixed idea; an obsessive notion.

4. Mathematics.

   1. an arbitrary set of elements of a group.

   2. a collection of simplexes having specified properties.

5. 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.

6. 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.

complex British  

/ ˈkɒmplɛks /

adjective

1. made up of various interconnected parts; composite

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

3. grammar

   1. (of a word) containing at least one bound form

   2. (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

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

4. maths of or involving one or more complex numbers

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noun

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

3. informal an obsession or excessive fear

   he's got a complex about cats

4. 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

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

Usage

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

Other Word Forms

Derived Forms

• complexness
  noun
• uncomplexness
  noun
• overcomplex
  adjective
• quasi-complex
  adjective
• supercomplex
  adjective
• uncomplex
  adjective
• complexly
  adverb
• quasi-complexly
  adverb
• uncomplexly
  adverb

Inflected Forms

Nouns

• complexes
  plural

Etymology

Origin of complex

First recorded in 1645–55; 1905–10 complex 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

Explanation

People who are really good at math can handle complex math problems. The rest of us are all set with simple stuff like the times tables. Use complex to refer to something that is not simple. Something complex has two or more related parts, or is not simple in its structure. As a noun, a complex is a group of units, often a group of buildings. The adjective is stressed on the second syllable, but the noun is stressed on the first syllable. Complex is from Latin complexus, from complecti "to encircle or embrace."

Example Sentences

See Examples For:

complex complexes

Early communities may contain relatively harmless bacteria, while more complex communities can eventually include species strongly associated with gum disease.

From Science Daily ● Oct. 7, 2026

For Md Zahedul Hasan, managing director of state-owned Nuclear Power Plant Company Bangladesh, the giant complex represents the culmination of a decades-old ambition to bring nuclear power to the country.

From Barron's ● Oct. 7, 2026

The complex internal hierarchy of Israel’s kibbutzim ensures that only a few long-term residents—usually older people—have a vote in matters relating to governance, including the painful question of knocking down the houses of the kibbutz.

From The Wall Street Journal ● Oct. 6, 2026

The clouds were made in the Netherlands by a firm with a history of building steel ship hulls that now specializes in building complex steel constructions like the clouds using digital data.

From Los Angeles Times ● Oct. 6, 2026

I take the long way around the complex to get back to reception, avoiding the hallway that leads to Mr. Harris’s old room.

From "Red Flags and Butterflies" by Sheryl Azzam

Up to now, this area has barely been studied in comparison with famous nearby sites such as the Valley of the Kings and the large temple complexes of Luxor and Karnak.

From Science Daily ● Sep. 10, 2026

On Friday, lawmakers agreed on a compromise on proposed legislation to regulate energy use by California’s growing data center industry, measures prompted by community fears about the massive complexes.

From Los Angeles Times ● Sep. 1, 2026

SpaceX’s new spaceport will be the largest in the world, with five launch complexes, each equipped with two pads.

From MarketWatch ● Aug. 25, 2026

Since the June 2025 attacks, satellite images show the tunnel complexes remain sealed.

From The Wall Street Journal ● Jul. 25, 2026

Luma called again, raising her arm in the air and pointing in the direction of the apartment complexes north of the field.

From "Outcasts United: An American Town, a Refugee Team, and One Woman's Quest to Make a Difference" by Warren St. John

Related Words

• complicated
• convoluted
• disturbing
• intricate
• obscure
• perplexing
• sophisticated