It's not just one thing.

I find when I tell people I have ADHD they seem a bit perplexed. I might get a direct response of "You're not hyperactive. Are you?", or an indirect one like "isn't that, like being hyperactive?" implying that they didn't think I was hyperactive, then there's the disbelieving response of "isn't that something kids get?", and the denial "Oh really?".  I can understand where they're coming from because if you told me I had ADHD  a decade ago, I probably would have laughed, a bit like when you think you're having an "OCD" moment (which incidentally has a number of different types and symptoms and is more than just needing to make things straight or in order).

If I told someone I had a cold, they'd expect maybe a sore throat, blocked or runny nose, perhaps sneezing, a cough, a hoarse voice and that I might be generally feeling unwell.  If I didn't have a cough they wouldn't look at me in disbelief. A cold is more than just a cough, or sneeze and similarly ADHD is more than just hyperactivity. In fact in adulthood, hyperactivity is more internalized, but can manifest in other ways like jiggling of legs, or tapping fingers, clicking pens, much to the annoyance of your colleagues. It can also feel like you just have to get up and do something but you have no idea what. So as an adult you may not appear to be hyperactive.

I'm not going to list all the symptoms here because there is plenty of sites that already have it, and I'll probably mention them in future posts, but like a cold, you don't have to have all of them to have ADHD and some of them might be worse than others. Oh, and there's 3 types of ADHD too.