com·plex
ˈkäm-ˌpleks 
1
: a whole made up of complicated or interrelated parts
a complex of welfare programs
the military-industrial complex
2
a
: 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
kəm-ˈpleks,
ˈkäm-ˌpleks
1
a
: 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
complexly
adverb
complexness
noun
Did you know?
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”).
Synonyms
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
Nate Gartrell, The Mercury News, 13 Nov. 2024
Officers found Lorenzo-Olivera, 36, about 1:45 p.m. June 24, 2022, lying face down in a parking lot of an apartment complex at 1299 Electric Ave.
—Ron Wood, arkansasonline.com, 6 Nov. 2024
Tribune Content Agency, The Mercury News, 14 Nov. 2024
But with practice, these simple actions evolved into more complex behaviors, such as steering the car toward a specific destination.
—Kelly Lambert, Discover Magazine, 14 Nov. 2024
See all Example Sentences for complex 
Examples are automatically compiled from online sources to
show current usage.
Read More
Opinions expressed in the examples do not represent those of Merriam-Webster or its editors.
Send us feedback.
Noun
Lambert lived in an apartment complex on the 1400 block of 7th Street, where the shooting took place.
—Nate Gartrell, The Mercury News, 13 Nov. 2024
Officers found Lorenzo-Olivera, 36, about 1:45 p.m. June 24, 2022, lying face down in a parking lot of an apartment complex at 1299 Electric Ave.
—Ron Wood, arkansasonline.com, 6 Nov. 2024
Adjective
The relationship between cannabis use and other substance use behaviors is complex and multifaceted.
—Tribune Content Agency, The Mercury News, 14 Nov. 2024
But with practice, these simple actions evolved into more complex behaviors, such as steering the car toward a specific destination.
—Kelly Lambert, Discover Magazine, 14 Nov. 2024
See all Example Sentences for complex
Dictionary Entries Near complex
Cite this Entry
“Complex.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/complex. Accessed 28 Nov. 2024.
Copy CitationKids Definition
complex
1 of 2 noun
com·plex
ˈkäm-ˌpleks
1
: a whole made up of many complicated or related parts
2
: a system of thoughts, feelings, and memories that exist in one's mind but of which one is not aware and which influence one's behavior
3
: a building or group of buildings housing related units
an apartment complex
complex
2 of 2 adjective
com·plex
käm-ˈpleks
kəm-;
ˈkäm-ˌpleks
1
a
: composed of two or more parts
a complex mixture
b
: consisting of a main clause and one or more subordinate clauses
a complex sentence
c
: formed by union of simpler substances
2
: having many parts, details, ideas, or functions often related in a complicated way
a complex problem
a complex machine
complexly
adverb
Medical Definition
complex
1 of 3 adjective
com·plex
käm-ˈpleks
kəm-ˈ
kəm-ˈ
ˈkäm-ˌ
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
complex
2 of 3 noun
com·plex
ˈkäm-ˌpleks
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
complex
3 of 3 transitive verb
com·plex
käm-ˈpleks
kəm-ˈ
kəm-ˈ
ˈkäm-ˌ
1
: to form into a complex
RNA complexed with protein
2
: chelate
: to form a complex
hormones which must complex with specific receptors
Love words? Need even more definitions?
Merriam-Webster unabridged
Share