coinsurance

noun

1. (US, countable, especially, uncountable)The joint assumption of risk between the insurer and the insured party.
2. (US, countable, especially, metonymically, uncountable)The amount paid by the insured in accordance with this risk sharing.

   “For Part B-covered services, you usually pay 20% of the Medicare-approved amount after you meet your deductible. This is called your coinsurance.”

3. (countable, uncountable)The joint assumption of risk between multiple insurers.