“Complex” != “Complicated”

I’d like to take an aside to discuss two commonly interchanged words: “complex” and “complicated”. I’d assert that the two words, while commonly considered equivalent, are - in fact - quite different.

What is “Complex”?

Something complex is something composed of many interconnected interacting components. Having a full understanding of a complex system requires having at least a high-level understanding of its constituent components, but having a high-level understanding of such a system rarely requires understanding each underlying component in detail.

This is the primary idea behind abstraction. When we wish to hide the complexity associated with a system we make the components of the system opaque and reliable. Still, this does not remove the fact that the underlying problem or corresponding solution may be complex.

As an example, most high-level languages feature garbage collection, which is a very complex solution to a very complex problem. Still, we do not bemoan a garbage collector for being complex (unless you have the delightful task of implementing garbage collection, then you have a free pass to bemoan its complexity while you struggle with the intricacies involved with building that complex system).

We can attribute a quality of complexity to a problem or system, and when it surpasses some arbitrary threshold, we say that it is complex problem or system.

One thing to keep in mind is that complexity is not intrinsically bad. For this reason, I avoid saying something is “too complex” as too imply that its complexity should be reduced below some arbitrary threshold. When I wish for something to be less complex, I prefer another word:

What is “Complicated”?

Here, when I say “complicated”, I use it as the past-tense form of the verb “complicate”. When we complicate something, we introduce complexity which was not already there, and we often imply that such additional complexity was not required. A system that is complicated is also complex, but that complexity has been introduced by some other person or system (usually unnecessarily).

Being complex is an intrinsic property of a problem or system, but being complicated means something that has been added (for the worse).

For this reason I prefer to keep a distinction between “complex” and “complicated”, and will avoid using the one term when I really mean the other.

How Does this Affect Me?

Here is an aphorism taken from Tim Peters’s The Zen of Python:

Simple is better than complex.
Complex is better than complicated.

We should strive for simplicity. Abstractions are meant to make complex things simpler, and a good abstraction will succeed in doing so, even if some complexity remains. Just because some complexity remains in an abstraction doesn’t mean the abstraction has failed: it may mean that the underlying problem is too complex to allow trivial solutions. Complex problems demand complex solutions.

Too often we will throw up our hands a decry something as “unnecessarily complex,” when such complexity is demanded by the underlying problem. Instead, we should learn to recognize when something has been complicated and work to remove (and avoid adding) any unneeded complexity.