eternity

Eternity is the concept of existence or duration without beginning or end. It is used in two related senses: timelessness, in which something is not subject to temporal change; and infinite duration, meaning an endless sequence of moments that extends without limit.

In philosophy of time, eternalism holds that all moments in time—past, present, and future—are real, while presentism holds that only the present moment exists. Some accounts follow Boethius, defining eternity as the complete, simultaneous presence of all moments of life, rather than a long duration.

In theology, eternity is often attributed to God or the divine: being eternal, existing beyond time, and often described as immutable and necessary. Debates continue about whether the divine is timeless or everlasting in a way that preserves ongoing action within time.

In science, time is a physical dimension in relativity, and cosmology raises questions about whether time had a beginning. Eternity is generally treated as a philosophical or theological notion rather than an empirical property of the universe.

Outside philosophy and religion, eternity is used metaphorically in literature and culture to denote permanence, the unchanging, or experiences measured as lasting beyond ordinary time.