What is he meaning of the prefix 'N'?

Answer 1

It can mean different things; among other things, a lowercase "n", used with units, means "nano" - a multiple of 10 to the power -9 (i.e., a billionth).

Answer 2

The prefix 'N' typically denotes negation or absence in words. It is often used to indicate that the following word has a negative meaning or expresses the absence of something. For example, 'nonchalant' means not showing any concern, 'nonfiction' means not based on imaginary events.