kiwen

kiwen are things whose form resists changing. This is almost always a hard physical material or object, like a rock or wood or crystal. It can describe something's material, so a chair made out of a hard material could be kiwen. kiwen can be brittle. Some rocks break apart easily, but they're still kiwen. But there are many brittle things that are not kiwen, so while kiwen can refer to brittle things, it never means "brittle."

It is additionally possible to talk about nonphysical things using kiwen, but it's imperative to explain your metaphor clearly. Ask two toki ponists about what kiwen means metaphysically and you'll get three answers. None of them are universally intuitive. Without this extra expansion, it's a good idea to avoid using kiwen to talk about non-physical things.