In aeternum, "forever," expresses temporal infinitude, duration without terminus. In poetry, this phrase appears in vows, curses, and claims about permanence. Poets invoke it when promising eternal love, when claiming poetry's immortality, or when contemplating endless punishment or reward. The phrase suggests both comfort and terror—eternal bliss or eternal suffering, depending on context. It appears in love poetry, epitaphs, and religious verse, where speakers either celebrate or fear forever, where they make promises they cannot verify, where they attempt to conceive what cannot truly be imagined—existence without end, love without limit, duration that never exhausts itself, time that never runs out, relationship that never terminates.

In aeternum appears frequently in liturgical Latin and ecclesiastical writing, giving it strong theological resonance. In poetry it can suggest divine timelessness, enduring love, or the illusion of permanence contrasted with mortal fragility. Students should note its ablative construction implying duration without limit. It pairs effectively with terms such as semper and ad infinitum, though the former stresses continuity and the latter abstraction.