What is the meaning of "myriad"? Is this word a noun or an adjective?
Myriad can be either a noun or an adjective depending on use. Its meaning is connected with a great number of something.
As a noun it means a great number of something and can be used in a sentence like:
Internet is connecting a myriad of computers
As an adjective it means countless or great in number and could be used in a sentence like:
the myriad lights of the city