The sum which the insured pays periodically to his insurance company is called

The sum which the insured pays periodically to his insurance company is called a premium.

Explanation:
When you purchase an insurance policy, whether it's for health, life, car, or any other type of insurance, you agree to pay a certain amount of money at regular intervals to the insurance company. This amount is known as the premium. The premium is the cost you pay to the insurance company so that they will provide you with coverage and financial protection against specified risks.

Insurance companies calculate your premium based on various factors including the type of insurance, the amount of coverage you want, your age, your health (for health or life insurance), and other risk factors. In return for paying your premium, the insurance company promises to cover certain costs or losses as outlined in your policy.