What is the best definition of empire

Roman Empire:

noun

the lands and peoples subject to the authority of ancient Rome.

the form of government established in ancient Rome in 27 b.c., comprising the Principate or Early Empire (27 b.c.–a.d. 284) and the Autocracy or Later Empire (a.d. 284–476).

a later empire, as that of Charlemagne or the Byzantine Empire, regarded as a restoration or continuation of the ancient Roman Empire or one of its branches.

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dylan has written many enduring songs and he has received several awards for his musical achievement;  

any written work with artistic value can be considered literature; especially if such work is publicly recognized, and has had importance and endurance among people; whether is poetry or fiction or drama or even criticism, since it's the transcendence and representation of a culture, language or people in a period of time to more people, using letters (words), regardless the subject.

the nobel prize in literature is given to authors from any country based on a body of work as a whole that inspires and nurses the life of humanity.  

and the work of bob dylan matches that description, therefore is well deserved since he'd created new poetic expressions within the american song tradition, that has inspired and influenced the lives of many people, not only withing the united stated but worldwide as well.