Define literary allusion and an appositive. How is the title of Shelley's classic novel both an allusion and an appositive?

An allusion is a evocation of a particular thing or person ("She is his Achilles' heel"), and an apposition occurs when two nouns or noun phrases form a syntactic unit (as in "Madrid, capital of Spain").

The title of Mary Shelley's classic novel is Frankenstein, or The Modern Prometheus (you could actually think of it as a title and a subtitle) and it tells the story of the young scientist Victor Frankenstein, who creates an atrocious creature in one of his experiments. The title is made of a noun and a noun phrase, and it links Frankenstein to the immortal hero Prometheus, since both were geniuses whose experiments ended in tragedy. In Greek mythology, Prometheus was a Titan credited with creating a man from clay. He also stole the fire and gave it to humanity, and for that reason he was severely punished by the gods. Frankenstein's creature became a monster, and after being abandoned by his creator, he decided to take revenge.