Complex vs complicated

Have you ever wondered what the subtle distinction is between these two adjectives? Or perhaps you’ve even used both of them in the same sentence (This is a complex, complicated procedure’) without really knowing what the difference is. Let’s see if we can disambiguate.

Dictionary definitions

My first port of call when writing RyR posts is usually the dictionary (several dictionaries, in fact: one British English, and one American English).

In this case, the dictionary is largely unhelpful.

It defines complex as ‘difficult to understand or explain because of having many different parts’, and complicated as ‘involving a lot of different parts, in a way that is difficult to understand’.

In other words, you might expect them to be synonymous.

However, in practice, they have different connotations (at least, I think so!).


Complexity is about how many parts there are to a system (or argument, thought process, etc.).

For this reason, things are often described as complex when they are highly technical or intellectually demanding.

However, although it may sound counterintuitive, a system might simultaneously be both complex and straightforward (although not simple, because simple is the opposite of complex).

Let’s imagine you’ve designed a board game with lots of rules; or a management structure for an organisation that has many parts to it. These things could still be straightforward in the sense that they are easy to explain, or the rationale behind them is very clear.


To me, the word complicated implies a value judgement.

When you say something is complicated, you mean that you are finding it hard to understand, or you would struggle to explain it to someone else.

Complicated refers to to difficulty, rather than degree of detail.

In a way, there is an implied ‘too’ in there: complicated means ‘too difficult’.

This is why the word complicated collocates well with adverbs such as overly, excessively, or unnecessarily.

Because of the implicit value judgement (complicated = ‘I find this hard to follow’), I would argue that complicated is a little derogatory.

The book’s plot was so complicated I got bored.

The rules of this board game are really complicated.

Description vs opinion

From what I’ve written so far, perhaps you will be able to see why the word complex is usually descriptive, whereas complicated expresses an opinion.

Here are some typical examples of the word complex:

She underwent a complex surgical procedure.

The question of who is legally responsible is a complex issue.

If you’re in a meeting situation and you want to use a word that is descriptive and neutral, in a reasonably high register sentence, then go with complex.

Compare the example sentences (from the Cambridge Dictionary) for complicated:

His lecture was complicated and difficult to follow. (judgement/negative opinion).

Our lawyer guided us through the more complicated questions on the form. (i.e. difficult to understand – perhaps the language was difficult)

The road system was so complicated that we had to stop several times to find our bearings. (i.e. difficult to grasp)

Your conclusion is good, but the final sentence is too long and complicated. (value judgement/opinion)


Sometimes things can be both complex and complicated.

For example, the workings of a machine might be complex – with a lot of moving parts – and complicated – hard to understand unless you are a mechanic or engineer.

If you’re trying to work out where the difficulty comes from (from the complexity of the system/argument/machine or from its being complicated), ask yourself whether the relevant factors are internal or external.

Complexity is generally something internal, i.e. it’s part of the design of an object, whereas there are many external factors that could contribute to something being complicated. For example, someone could have complicated ideas because they’re very roundabout, or their explanations are illogical or use difficult language. A question on a form could be complicated because you need various bits of information such as your social security number and passport number, so you can’t find the answer quickly. The rules of a game might sound complicated because every time someone plays their turn, there are too many steps involved and it’s easy to lose track. A relationship could be complicated because there’s a lot of history or baggage involved (i.e. previous events that have made emotions run high).

I hope these examples have made it easier for you to distinguish between these two words.


The list of synonyms of complicated backs up the idea that it’s a word that expresses a negative opinion:

  • difficult
  • hard
  • arduous
  • convoluted
  • intricate
  • perplexing
  • problematic
  • troublesome
  • entangled
  • puzzling
  • abstruse
  • Byzantine
  • labyrinthine
  • recondite

Synonyms of complex include:

  • complicated
  • convoluted
  • composite
  • multiple
  • elaborate
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