Co-insurance typically indicates what type of payment relationship?

Co-insurance involves a payment structure in which both the insurer and the insured share the costs of covered expenses. This means that after the insured meets their deductible, they are responsible for a certain percentage of the costs, while the insurer pays the remaining percentage. This arrangement encourages policyholders to be more aware of their healthcare expenses because they have a financial stake in the costs incurred.

In contrast to full coverage where the insurer pays all expenses after the deductible is met, co-insurance requires the insured to cover part of the costs, typically a specified percentage. The first answer option discussing partial reimbursement may suggest that only some of the costs are covered, but it does not capture the essence of shared financial responsibility inherent in co-insurance. The fourth option about flat rate payments doesn't reflect the variable nature of sharing costs in co-insurance, where the insured's share is proportional to the total cost of services received. Thus, the definition of co-insurance as a shared cost arrangement between the insurer and the insured is aptly represented by the correct answer.