Final answer:
A monthly payment for pet health insurance is called a premium, which is separate from cost-sharing mechanisms like deductibles, copayments, and coinsurance.
Step-by-step explanation:
The correct answer to the question of what the monthly payment for a pet health insurance policy is called is the premium. Insurance terms such as deductible, copayment, and coinsurance are related to cost-sharing mechanisms that determine how much the policyholder will pay out-of-pocket when a claim is made. In contrast, the premium is a periodic payment made to the insurance company to keep the policy active, which is not tied to specific claims or incidents.