Well, when I say 'element', I refer to general 'things' that don't necessarily have a concrete form; example, while 'metal' qualifies as an element, thing like 'iron', 'silver', or even 'magnesium' count as well. Specificity would also lead to higher power relative to a more general attribute, so making a sword with 'iron' attribute is easier than 'metal', but 'metal' would be able to generate other things... If that makes sense.
By extension, 'water', 'fire', and all the classic 'elemental' stuff you see falls under this umbrella category, though obviously things have to scale in turn.
As for elements of the mind and things like 'aether', I'll run that on a case by case basis. For the most part, you might consider those in between 'concept' and 'element', leaning towards the former.