A poem mourning someone's death is related to Elegy

A poem mourning someone's death is related to Elegy.The Greek term elegeia originally referred to any verse written in elegiac couplets and covering a wide range of subject matter (death, love, war). The term also included epitaphs, sad and mournful songs,and commemorative verses.The Latin elegy of ancient Roman literature was most often erotic or mythological in nature. Because of its structural potential for rhetorical effects, the elegiac couplet was also used by both Greek and Roman poets for witty, humorous, and satiric subject matter.Other than epitaphs, examples of ancient elegy as a poem of mourning include Catullus' Carmen 101, on his dead brother, and elegies by Propertius on his dead mistress Cynthia and a matriarch of the prominent Cornelian family.

Ovid wrote elegies bemoaning his exile, which he likened to a death.
In English literature, the more modern and restricted meaning, of a lament for a departed beloved or tragic event, has been current only since the sixteenth century; the broader concept was still employed by John Donne for his elegies, written in the early seventeenth century. This looser concept is especially evident in the Old English Exeter Book which contains "serious meditative" and well-known poems such as "The Wanderer," "The Seafarer," and "The Wife’s Lament." In these elegies, the narrators use the lyrical "I" to describe their own personal and mournful experiences. They tell the story of the individual rather than the collective lore of his or her people as epic poetry seeks to tell.For Samuel Taylor Coleridge and others, the term had come to mean "serious meditative poem":Elegy is a form of poetry natural to the reflective mind. It may treat of any subject, but it must treat of no subject for itself; but always and exclusively with reference to the poet. As he will feel regret for the past or desire for the future, so sorrow and love became the principal themes of the elegy. Elegy presents every thing as lost and gone or absent and future.

A famous example of elegy is Thomas Gray's Elegy Written in a Country Churchyard .

"Elegy" may denote a type of musical work, usually of a sad or somber nature. A well-known example is the Élégie, Op. 10, by Jules Massenet. This was originally written for piano, as a student work; then he set it as a song; and finally it appeared as the "Invocation", for cello and orchestra, a section of his incidental music to Leconte de Lisle's Les Érinnyes.