lets you refer to a purportedly familiar name or fact in history or literature. Such reference differs from the use of an illustration in that it is less formal. M. H. Abrams defined allusion as "a brief reference, explicit or indirect, to a person, place or event, or to another literary work or passage" Poetry abounds in allusions. Shakespeare uses allusion very frequently. Martin Luther King, Jr
., alluded to the Gettysburg Address in starting his "I Have a Dream
" speech by saying "Five score years
"; his hearers were immediately reminded of Abraham Lincoln's
"Four score and seven years ago
", which opened the Gettysburg Address
. King's allusion effectively called up parallels in two historic moments.