The word myriad works both as an adjective and as a noun, but using it as an adjective is usually more concise.
For instance, in these sentences the words a and of could be removed from a myriad of with no loss of meaning:
There is unrest in Iraq as well, and a myriad of conflicting interests [and myriad conflicting interests] … [National Review]
The environmental reviews began in the summer of 2007 and included a myriad of public meetings [and included myriad public meetings] and ample avenues for public comment. [Buffalo Business Journal]
Applied to mass nouns
Because a myriad consists of a number of things, the word is illogical when applied to mass nouns. In the following sentences, for example, construction settlement and ’90s rap are mass nouns, so myriad doesn’t make sense:
Even this freeze has largely been ignored by the government, which has approved a myriad of settlement construction since the announcement … [Antiwar.com]
Since there was no radio in the truck, Tonia regaled us with a myriad of 90s rap while en route to our trailhead. [Huffington Post]
As a plural noun
When used as a noun, a myriad is singular. Consider this example:
But beneath that commercial success have been a myriad of bands who have never sold a million records but have amassed a loyal fanbase. [Stirling Observer]
Here, the noun technically associated with the first have is myriad (not bands), so this writer is incorrectly treating myriad as a plural noun. A better way to phrase this sentence would be, But beneath that commercial success has been a myriad of bands …
