What is the difference between 'complex' and 'complicated', in semantics and usage?
I guess 'complex' is more technical; it's used in math, physics, engineering, grammar, etc. But what about non-technical use? Is there any difference between the two sets of examples bellow?

  • We have a complex relationship.
  • He is a complex person.
  • This problem is complex.

  • We have a complicated relationship.

  • He is a complicated person.
  • This problem is complicated.

2 Answers 2


complicated is an adjective, while complex is either an adjective or a noun. The latter can be used to describe a structure:

The new pharmacy complex is currently being built.

A problem regarding the human body:

I was told I have a complex when I look down other people.

Also, a problem can be complex or complicated. Often a complicated problem is something more complex.

  • There is another difference worth noting - I feel that "complex" describes something regardless of the perspective. A complex concept is a concept that is incredibly intricate and precise. A complicated concept, however, is one that is difficult to understand from somebody's perspective. I might be reading too far into it though.
    – Alex K
    Dec 17, 2015 at 21:10

Things that are not easily explained or described are often referred to as either complex or complicated interchangeably in daily usage. The interchangeability does not result in any loss of understanding. However, there are differences in meaning of the two words.

Complex comes from the Latin an aggregate of parts
Complicate comes from the Latin to fold together

Complex refers to a single thread of idea or subject which has many different parts, but which make an identifiable whole This is shown when it is used in another way which describes a group of similar or related objects :

The hospital building complex
A personality complex

Complicated refers to how things interact or interconnect where there are several different factors involved :

The street layout is complicated
Relationships can be complicated

There was a recent movie entitled: It's Complicated

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