Can someone explain Hmmm [closed]
Solution 1:
It expresses doubt without being outright rude about it.
Solution 2:
It is somewhat a close relative of "ok" or "I am following". More like when someone is telling/informing you about something you'd says "hmmmm" to indicated that you're following what is being told.
"Ummm" on the other hand means that you are thinking trying to recall or a find an answer to something, usually a question.
It's usually contextual plus the meaning varies from one group or locality to another depending on tactic agreement they have come to make about what it refers to.