“Angels & demons” (03:53):
"The church is at a crossroads - so riven by change and dissent - its ancient traditions threatened by a modern world."
What meaning might the narrator be trying to convey by using “a” instead of “the”? Is it grammatically sound? Can zero article be used here(I hope not)?
The narrator is trying to convey the idea of an abstract, generalised 'modern world'. Any modern world, including (of course) the one we live in. We can use an indefinite article when it is not strictly relevant which thing we are talking about.
The indefinite article (a, an) is used before a noun that is general or when its identity is not known.
