Adonais was occasioned by the death of John Keats on 23 February 1821 and is ranked alongside John Milton's Lycidas (1638), Philip Sydney's Astrophel (1595), and Thomas Gray's Elegy Written in a Country Churchyard (1751) in the great tradition of English pastoral elegy. Shelley started writing Adonais some time after Keats's death, as he did not learn of the tragic event until 11 April 1821. Composition of his elegy for Keats was rapid and Shelley wrote, on 8 June 1821, to his publisher, Charles Ollier, that he had completed a poetical lament “of about forty Spenser stanzas” (Letters, 2, 297). To ease metrical scansion, Shelley added an extra vowel to the name of his poem's title and …
Sandy, Mark. "Adonais". The Literary Encyclopedia. First published 20 September 2002; last revised 30 November -1.
[http://www.litencyc.com/php/sworks.php?rec=true&UID=6843, accessed 25 April 2015.]