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

“As these off-balance sheet commitments become more frequent, larger, and more complex, it is becoming increasingly difficult for investors to assess companies’ total potential leverage,” Morgan Stanley accounting analysts wrote in April.

From The Wall Street Journal ● Aug. 17, 2026

Traditional approaches to studying cause-and-effect relationships are often not possible when investigating populations and ecosystems, which are large, complex and messy.

From Los Angeles Times ● Aug. 16, 2026

But sometimes the justices also put out a call for this complex to give them a reason to do something.

From Slate ● Aug. 16, 2026

The findings also help bring together recent research that has raised doubts about how important haplodiploidy really is to the evolution of complex insect societies.

From Science Daily ● Aug. 15, 2026

We call it “instrument flying” now, and it’s much more complex and reliable than it was in the 1930s.

From "A Thousand Sisters" by Elizabeth Wein

The Los Angeles Regional Water Quality Control Board voted to require shopping centers, warehouses, private hospitals and office complexes whose properties drain into the Dominguez and Los Cerritos channels to get stormwater permits.

From Los Angeles Times ● Jul. 29, 2026

"This tells the model which parts of the viral and host proteins are close to each other inside infected cells. This was especially useful for virus-host complexes, which are often difficult to predict reliably."

From Science Daily ● Jul. 21, 2026

But due to much of this World Cup using existing stadia, hotels, training complexes and travel infrastructure, "there won't be any economic benefits from development".

From BBC ● Jul. 16, 2026

One of Latin America's worst earthquake disasters hit hardest in the coastal La Guaira area north of the capital Caracas, where scores of residential complexes were flattened.

From Barron's ● Jul. 4, 2026

Two more missile complexes in Cuba would be ready to fire by the end of the day.

From "Fallout: Spies, Superbombs, and the Ultimate Cold War Showdown" by Steve Sheinkin

Related Words

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