無wú
means “not existing”
or “not having”
it is the opposite of 有yǒu
in modern chinese
無wú and 沒有méiyǒu mean the same thing
沒méi expresses negative
沒méi = not
so 沒有méiyǒu is “not have” or “not exist”
let’s take an every day example:
you walk into a café and ask:
“有沒有 wi-fi?”
“have-not-have wi-fi?”
(is there wi-fi?)
the response will either be
1. “有” meaning “have” or “exist”
as in
“the café has wi-fi”
“wi-fi exists in the café”
or
2. “沒有” (無wú)
“the café does not have wi-fi”
“wi-fi does not exist in the café”