eternal

Synonyms: abiding ageless always amaranthine boundless ceaseless constant continual continued continuous dateless deathless enduring everlasting forever illimitable immemorial immortal immutable imperishable incessant indefinite indestructible infinite interminable lasting never-ending perdurable perennial permanent perpetual persistent relentless termless timeless unbroken unceasing undying unending unfading uninterrupted unremitting without end

Antonyms: brief changeable changing ending ephemeral stopping temporary terminable transient