complex
Noun pluralcomplexes
Pluralcomplexes
Formscomplexes, complexing, complexed
- 1Hard to understand or deal with because it has many parts or details.
Like a puzzle with so many pieces that it is hard to put together.
The instructions were too complex for the children to follow.
Tax forms can be complex and confusing for first-time filers.
UsageSay very complex; complicated means nearly the same.
Similarcomplicated, intricate, difficult, involved, hard
Oppositesimple, easy, basic, straightforward
Note
- 2A group of buildings that are used together for one purpose.
Like a small town where every building belongs to one school or company.
The sports complex has a pool, a gym, and tennis courts.
They built a new housing complex near the river last year.
UsageSay a sports complex or a housing complex.
- 3Made of many different parts joined together rather than a single piece.
Like a model built from hundreds of small bricks fitted together.
A car engine is a complex machine with many moving parts.
The human body is complex, built from many systems working together.
UsageSay more complex and most complex.
Similarcomposite, compound, intricate, complicated, elaborate
Oppositesimple, basic, elementary, uncomplicated
Note
- 4A strong worry or fixed feeling about something that affects how a person thinks and acts.
Like a worry that gets stuck in your mind and will not leave.
He has a complex about his height and hates being teased.
She developed a complex about speaking in front of large groups.
UsageSay someone has a complex about something.
Note
- 5A chemical unit of atoms or molecules held together, like a metal atom surrounded by molecules, or proteins joined as one.
Like a center piece with smaller pieces lightly clipped around it.
Iron forms a complex with the molecules around it in your blood.
The metal complex changes color when it reacts with the solution.
Note
- 6A group of connected things that work or are thought of together.
Like a bunch of related things grouped under one name.
Poverty, poor schools, and crime form a complex of linked problems.
A whole complex of problems came up during the move.
UsageSay a complex of problems.
Similarnetwork, system, web, cluster, combination
Note
Less common meanings
- 7In mathematics, using numbers made of a real part and an imaginary part.
Like a number built from two pieces, a real one and an imaginary one.
The equation turned out to have two complex roots instead of real ones.
In math class we learned how to add and multiply complex numbers.
Note
- 8A group of very similar species that are hard to tell apart.
Like a set of twins who look the same but are not the same person.
Scientists say these look-alike beetles form a complex of four species.
Botanists split the old plant complex into several distinct species.
Note
- 9
- 10A number made of a real part and an imaginary part.
The interesting aspect here is that U₃ is irreducible, even though all irreps over the complexes are one-dimensional because ℤ₄ is abelian.
1996, Barry Simon, Representations of Finite and Compact Groups - 11A group of wildfires burning close together at the same time.
- 12A group of thunderstorms that move and act together as one large system.
- 13To make something more complicated or harder to deal with.
- 14A word made of several parts, like a root with prefixes or endings added.
- 15Used for a shape whose lines cross over each other.
Showing meanings only.
Practice
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Origin
From French complexe, from Latin complexus, from a verb meaning to entwine or wrap around. It comes from parts meaning "together" and "to weave."
Checked 31 Oct 2026 · 3 facts
- English complex comes from French complexe, from Latin complexus. en.wiktionary.org
- Complexus is a past participle of complector; the infinitive meaning to entwine or wrap around is complecti. en.wiktionary.org
- The underlying Latin components mean together and to weave. en.wiktionary.org