Final answer:
An allusion is a reference to a person, place, or thing outside of the text.
Step-by-step explanation:
An allusion is a reference to a person, place, or thing outside of the text. It is an expression designed to call something to mind without mentioning it explicitly. For example, in Hamlet, when the character describes his father as 'Hyperion' and Claudius as a 'satyr,' he is making allusions to Greek mythological figures.