아무-도
'아무' indicates 'randomly choosing one among many other things' or 'not limiting the range of the object related to the following noun.' If a noun modified by '아무' adds to a postposition '도', it becomes a negative sentence in full denial and makes the latter sentence a negative one. The auxiliary '도' can be used before other postpositions. If a noun is a person, it is used as a form of 'of 무도', '아무에게도', '아무한테서도' without the noun.
Example:
1. 그 사실은 아무도 모릅니다.
Nobody knows about the truth.
2. 아무 도움도 주지 못해서 미안할 뿐입니다.
I just feel sorry not to give any help.
3. 아무한테도 연락하지 않았어요.
I didn't contact anyone.
4. 어제부터 아무 것도 먹지 않았어요.
Haven't eaten anything since yesterday.
5. 방학 때 아직 아무 계획도 없어요.
I don't have any plans yet for the vacation.
6. 제가 할 테니까 아무 준비도 하지 마세요.
I'll do it, so don't prepare anything.