To make something eternal, preserve it permanently, or cause it to last forever (American spelling of eternise).
From eternal plus -ize suffix (American spelling of -ise). Both forms derive from Latin aeternalis, with -ize being the standard American suffix for creating verbs from adjectives.
When you eternize your love through marriage vows, you're using language to try to lock something changing and temporary into something permanent—which is why breakups feel like the betrayal of eternity itself.
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