... then I tend to assume you don't really understand it.
I have found again-and-again that when I can't find a straightforward, clear way to explain something, it means that I don't fully understand the concept myself. I experienced this a few days ago when replying to a colleague's request for information about a particular feature in a new product we're working on.
I started to write a reply, only to find myself writing longer and longer sentences, with parentheses inside parentheses and qualifications, exclusions and special cases galore.
I stepped back and realised that my problem was that I couldn't articulate - even to myself - what the core purpose of the function was. I was able to explain how to use it. I was able to describe when and where it would and wouldn't work but I couldn't say what it was for. That is: I couldn't tell a story to explain why it was even put there in the first place. What was going through the architect's mind? What problem were they trying to solve?
Once I did this thought experiment, I rapidly realised what it must be for... a bit of research and a couple of Sametimes later and I was done. I had a crisp explanation that told a good story and which made sense.
I was thinking about this last night when I thought: "How do I explain my job?" I currently have two 'stories' for my job: the one I tell non-IT people (family, friends, etc) and the one I tell IT people. The first one explains what an IT consultant does in a general sense. The second story assumes this knowledge and concentrates on what differentiates my job from other consulting roles.
I realised that neither of them was satisfactory and resolved to use the pages of this journal to rectify the problem.
Accordingly, I have set myself the task of crisply describing what it is, exactly, that I do... in a way that is accurate, understandable and interesting. I don't promise to be quick but I will get there...