Definitions of elegy poems, or elegiac poetry, are quite consistent. The elegy derives from the original Greek and Roman laments or "complaints" written in alternating pentameter (i.e., five metric feet) and hexameter (i.e., six metric feet) lines. The subject matter of later elegies may be the same as that of the Greco-Roman elegies: "complaints about love, sustained formal lamentations, or somber meditations" (Wheeler). The most usual subject is a "formal lament for someone's death" (Lynch).
According to Wheeler, the standard characteristics of the elegy of mournful lament are several. (1) Elegies have a first person poetic speaker (2) who invokes a Greek or Roman Muse while it (3) employs classical mythological allusions, as Milton does in Lycidas: "That from beneath the seat of Jove doth spring." The poetic speaker (4) questions fate and justice in the face of death and, if a Christian elegy, questions Providence. The speaker also (5) digresses to discussing his/er own feelings or life. The (6) digression provides the opportunity for the speaker's thoughts to clear and attain an enlightened understanding that rises above lament. (7) There is no story plot, and (8) the conclusion of the poem offers the insight of epiphany and consolation.
"Mid-Term Break" by Heaney is a mournful lament that breaks with the above characteristics in that there is no invocation to a Muse nor are there classical mythological allusions. Two allusions in the first stanza combine a college schedule with the death knell of church bells at a funeral: "Counting bells knelling classes to a close."
"Break, Break, Break" by Tennyson is likewise a mournful lament that breaks with the expected characteristics of an elegy. The invocation is not an appeal to an Muse but an apostrophe to the sea: "O Sea!" The allusions Tennyson employs are nautical ones: "the fisherman's boy"; "the sailor lad"; "he sings in his boat on the bay."
Both elegies are told in first person, but "Mid-Term" has a story plot with a surprise ending. At first we don't know who is being lamented. We only know:
In the porch I met my father crying--
He had always taken funerals in his stride--
After a the speaker's prolonged journey from the porch through the kitchen to "the room," we discover the lament is for the speaker's 4-year-old brother who was killed by a car:
No gaudy scars, the bumper knocked him clear.
A four foot box, a foot for every year.
From the last two lines, it is clear that Heaney's lament, though it might be said to have a brief digression to the speaker’s personal experience (stanzas 3-4), does not end in higher understanding and consolation--unless the absence of scars and marks can be seen as consolation.
"Break" has a story plot as well, albeit a short one, though it has nothing that might be seen as a personal digression. The speaker wishes his "tongue could utter / The thoughts that arise" in him. After watching the sights of the sea, he longs "for the touch of a vanished hand / And the sound of a voice that is still." The story ends with his repeated cry of "Break, break, break" and his lamentation that "the tender grace ... / Will never come back" to him. The speaker may be said to have had an epiphany of enlightened thought in his musings about the sea and the "stately ships" that go on their way to "their haven under the hill," but there is certainly no consolation for him at the end of his lament: "Will never come back to me."