What does "coinsurance" represent in health insurance?

Coinsurance represents the portion of healthcare costs that the insured must pay after reaching their deductible. It is typically expressed as a percentage of the total cost of a service, meaning that once the insured has satisfied their deductible requirements, they are responsible for a specific percentage of the expenses incurred. For example, if a patient has a coinsurance rate of 20%, they would pay 20% of the costs associated with a medical service or prescription while the insurance covers the remaining 80%. This system helps share the financial responsibility between the insurer and the insured, mitigating the total out-of-pocket expenses for the patient after their deductible.