Plural of copremium; a financial arrangement where two or more parties share premium payments for insurance or risk coverage.
From co- (together) + premium (price paid for insurance), from Latin praemium meaning reward. The plural form adds -a following Latin neuter noun patterns.
Insurance companies created this term to describe shared-cost plans that became popular in the 20th century—it's essentially the insurance world's version of splitting a bill with friends, but formalized into legal contracts.
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