Synonyms for Eternal:

adj.

abiding (adjective)
persistent, enduring.
around-the-clock (adjective)
at all times.
ceaseless (adjective)
endless, nonstop, round the clock.
continual (adjective)
aeonian.
continuing (adjective)
unending.
durable (adjective)
enduring, long-life, perpetual, livelong, everlasting, incessant, interminable, long, lifelong, prolonged, lengthy, perennial, lifetime, lasting, durable.
endless (adjective)
immeasurable, unbounded, limitless, countless, incalculable, unlimited, numberless.
enduring (adjective)
ageless.
eternal (adjective)
ceaseless, relentless, uninterrupted, illimitable, indestructible, immemorial, ageless, permanent, boundless, interminable, immortal, Termless, always, unending, indefinite, unbroken, lasting, enduring, timeless, incessant, persistent, amaranthine, continuous, forever, perennial, continual, unceasing, infinite, everlasting, perpetual, constant.
important (adjective)
crucial, fundamental, central, significant, major, vital, important, key, serious, meaningful.
infinite (adjective)
illimitable, timeless, numberless, unlimited, incalculable, immemorial, innumerable, perpetual, Termless, bottomless, everlasting, infinite, limitless, unbounded, countless, interminable, immeasurable, boundless, endless, inexhaustible, ceaseless.
never-ending (adjective)
ceaseless.
perpetual (adjective)
enduring, interminable, incessant, uninterrupted, permanent, endless, unceasing, continual, everlasting, lasting, constant, infinite, ceaseless, immortal.

n.

nonstop, continue, protracted, long-drawn-out, round the clock, ongoing, day in day out, around the clock, lingering. Eterne, change. world without end, amaranthine. eternal (noun)
immortal, everlasting, perpetual, interminable, eonian, unceasing, aeonian, permanent, unending, ageless, lasting, endless, long.

Other synonyms:

round the clock, world without end, Eterne, amaranthine, around the clock. ongoing, nonstop. relentless, persistent. endless
continuous.

Usage examples for eternal

  1. This eternal life of the soul, that lying promise of religion, is only true through our children. – The Shadow of the Cathedral by Vicente Blasco Ibañez
  2. " Well, and did they make you sleep, as usual, at the Crown, with the same eternal excuse, after having brought you fifty miles from town, of small house- no beds- all engaged- inn close by? – Pelham, Complete by Edward Bulwer-Lytton Last Updated: March 16, 2009
  3. Oh, for one eternal unconscious sleep! – Wilfrid Cumbermede by George MacDonald