what is allusion?

definition

Allusion is making a reference to another well known text from within one.

example

In the film Avatar, the central character Jake describes himself as being from the Jarhead Clan. Jarhead is a biographical war film published in 2005. The word Jarhead was originally used to refer to United States marines soldiers. 

explanation

When this technique is used, it calls to mind a whole set of ideas rather than just one. The messages and ideas from the other book or film are immediately conjured up in the mind of the reader or viewer. In the above example, the viewer is reminded that Jake is still a U.S. marine, despite the fact that he is living in the body of a Na'vi avatar. In typical style of 'allusion', the reference is made 'in passing', as if it is not important. However, the viewer understands a lot more by Jake's comment that he belongs to a 'tribe' and understands the association that he is still a 'soldier'.