As far as I understand, the -ㅁ ending can be added to a verb to make a noun representing a ‘completed’ or ‘embodied’ action. for example:
말하다 means to speak, 말씀 means speech.
만나다 means to meet; 만남 is a meeting.
죽다 is to die; 죽음 is death.
Can -ㅁ be added to descriptive verbs as well, like 예쁘다 → 예쁨? would that mean something like 'prettiness' or beauty? what about 크다 → 큼, meaning 'bigness' or 'having a large size'?
Finally, what about the copula, 이다, and its negative 아니다? can 'ㅁ' be attached to make '임' and '아님'? If so, how could those be used?