Is Forgetting Dementia?

Forgetting things is common for me, like trivial stuff, that's natural. But today my aunt mentioned she'd forgotten all her math from the past few years. Is it possible I have dementia? I don't know if she was joking. But for me, after graduating from school, if I don't use it for work, it really does gradually fade away. This is forgetting, it has nothing to do with dementia! If you're still interested, you could just go to a bookstore, buy a self-study book, and maybe it'll come back, don't you think!?