What’s the difference between instant and instantaneous? Is there in fact a difference?

There are lots of pairs of words that mean the same thing, but one has a precise meaning and the other has a range of meanings. Now, if there are two words with subtly different meanings, I’m all for keeping both of them and retaining the richness of our wonderful language, etc. But when one just covers a subset of the other’s meanings, I’m not, to be honest, quite sure. At least here there seems to be a technical term lurking around which will keep the smaller (yet longer!) word going.

So, instantaneous, to cover the smaller meaning first, means being done or happening instantly. It does have a specific meaning in physics around being measured or existing at a particular time.

Instant means occurring immediately, as you would expect, as well as a precise moment in time or a very short time. It also means something that’s processed to allow it to be prepared quickly, in the case of food, mainly, Also, and I dimly remember this from when I learned to type in the Dark Ages, it means “of the current month” (your letter of the 16th instant) although surely no one uses that now?

Both of them come from the same original source, from Latin for “be at hand” (instare), but instantaneous came through medieval Latin, which added -aneus to the original instant (thank you, Oxford English Dictionary for that information). I would advise using instant unless you’re a physicist, just to save complication and make it easier to read.

You can find more troublesome pairs here and the index to them all so far is here.

This one was suggested by Neil Langley posting on my main Troublesome Pairs post.

So what is the difference between complex and complicated? Is there one?

The answer is that their meanings overlap. The main dictionaries in the US and UK (Oxford, Merriam-Webster, etc.) define complex using the word complicated, so the adjective complex means made up of many different parts, or complicated. Complicated means consisting of many interconnecting parts, or intricate. So very similar.

The noun complication moves on to describe something that makes something complicated, a complex state (there we go again) and in medical terminology, a disease or condition that is secondary to the main one but makes it worse.

Complex as a noun can mean a few more things – an interlinked system (the military-industrial complex), and then Oxford links but Merriam-Webster lists separately, a group of interlinked buildings. It also has a meaning in psychology of a group of emotionally significant but repressed ideas which cause an abnormal kind of behaviour or an abnormal state (a persecution complex), and by extension, a more pop-psych preoccupation or exaggerated reaction (I have a complex about spiders). There’s a chemical meaning to do with connections, too.

So the nouns vary, but if you’re describing something made up of lots of different things that might be a bit confusing or intricate, it can be complicated OR complex.

Having done some rooting about, I did discover this Washington Post resource claiming to delineate a difference.

You can find more troublesome pairs here and the index to them all so far is here.