Meaning & use
complex
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Meanings
adjectivecomparable
Having many connected parts or details, so something is difficult to understand or deal with.
Grammar: Compares with more/most complex: a more complex design. It is not the same as merely difficult.
Patterns
- a complex issue
- a complex system
- complex relationships
The tax form was complex because every answer changed the next section.
Their friendship survived several complex misunderstandings.
The engine is beautifully made but mechanically complex.
adjectivebefore a nountechnical
Made of several parts that are connected in an organized way.
Grammar: Usually comes before the noun: a complex structure. It describes composition rather than difficulty.
Patterns
- complex structure
- complex carbohydrate
- complex sentence
A complex sentence contains one main clause and at least one subordinate clause.
Starch is a complex carbohydrate found in bread and potatoes.
The architect drew a complex pattern of connecting bridges.
nouncountable
A group of connected buildings used for a particular purpose.
Grammar: Takes a plural: two sports complexes. Often used after another noun: shopping complex.
Patterns
- sports complex
- shopping complex
- apartment complex
The university built a new sports complex beside the river.
Our apartment complex has a garden, gym, and laundry room.
nouncountablespecialist
A strong set of feelings or ideas, often unconscious, that shapes a person's reactions.
Grammar: Usually appears in phrases like inferiority complex, not as a general word for any feeling.
Patterns
- inferiority complex
- superiority complex
- a complex about something
He developed a complex about speaking after one embarrassing presentation.
The character's superiority complex hides deep insecurity.
Word forms
| comparative | more complex |
|---|---|
| superlative | most complex |
| plural of noun | complexes |
Common combinations
- highly complex
- The surgery is highly complex and needs a specialist team.
- complex problem
- Climate policy is a complex problem with no single solution.
- complex process
- Learning a language is a slow, complex process.
- emotionally complex
- The film is emotionally complex but still easy to follow.
- complex relationship
- They have a complex relationship because they are rivals and cousins.
Synonyms and how they differ
- complicated
- Close in meaning, but often stresses difficulty or confusion more strongly than connected structure.
- intricate
- Suggests many delicate details, especially in patterns, designs, or plans.
- sophisticated
- Suggests advanced development and skill; it can be positive, while complex is neutral.
- elaborate
- Emphasizes careful, detailed construction, sometimes more than necessary.
Opposites
Word family
- complexity noun
- the state of having many connected parts.
- complicate verb
- to make something more difficult or less simple.
- complicated adjective
- difficult to understand because of many parts or problems.
Commonly confused: complex or complicated?
complex vs complicated
Complex describes connected parts; complicated emphasizes that something is hard because it is difficult or tangled.
Practice
Which word best completes the sentence: “The wiring diagram looked ___ because every switch connected to several lights.”?
Choose one answer.
Complex fits many connected parts that are hard to follow. Simple, single, and plain all suggest few parts or easy understanding, the opposite idea.
Make it your own
Write a sentence using “complex”, then check it and compare it with the examples above.