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

At the most basic level, a fever is the body’s response to something unknown, the beginning of a complex process that targets an infection to ultimately kill it.

From Salon ● Sep. 11, 2026

Young people in particular find summer work at the sprawling complex, which attracts large numbers of American visitors.

From Barron's ● Sep. 11, 2026

It offered Lucas a different parcel near the Letterman complex; he declined.

From Los Angeles Times ● Sep. 10, 2026

“Human skills remain even more important as AI takes on more complex work and reshapes fields in ways we can’t fully predict,” says Leah Belsky, OpenAI’s vice president of education.

From The Wall Street Journal ● Sep. 10, 2026

A recognition that humans are also dependent on the complex ecosystems we have so carelessly put into peril: dependent for food, for water, for shelter—for our very survival.

From "Camp Panda" by Catherine Thimmesh

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

Wellpointe has nine senior housing complexes in the San Fernando Valley, but it has had difficulty acquiring enough single-family homes in the area to significantly expand its presence, he said.

From Los Angeles Times ● Aug. 18, 2026

The plant employs around 1,000 people and is just one of many sprawling industrial complexes standing out starkly from the lush Appalachian Mountain landscape.

From BBC ● Aug. 12, 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

The town itself had a weather-beaten look to it, with closed stores, rusted-out cars, and worn apartment complexes lining the road, but it was still beautiful.

From "The Son of Neptune" by Rick Riordan

Related Words

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