definition
Insurance, in law and economics, is a form of risk management primarily used to hedge against the risk of a contingent loss. Insurance is defined as the equitable transfer of the risk of a loss, from one entity to another, in exchange for a premium（保险费）.
the principle-law of large numbers
The vast majority of insurance policies are provided for individual members of very large classes. The existence of a large number of homogeneous exposure units allows insurers to benefit from the so-called “law of large numbers,” which in effect states that as the number of exposure units increases, the actual results are increasingly likely to become close to expected results. There are exceptions to this criterion. Lloyd's of London is famous for insuring the life or health of actors, actresses and sports figures. Satellite Launch insurance covers events that are infrequent. Large commercial property policies may insure exceptional properties for which there are no ‘homogeneous’ exposure units. Despite failing on this criterion, many exposures like these are generally considered to be insurable.
types of insurance
A. life insurance
Life insurance provides a monetary benefit to a decedent's family or other designated beneficiary, and may specifically provide for income to an insured person's family, burial, funeral and other final expenses. Life insurance policies often allow the option of having the proceeds paid to the beneficiary either in a lump sum cash payment or an annuity.(趸缴或年缴）
B. property insurance
This tornado damage to your home would be considered an "Act of God" for insurance purposes. Property insurance provides protection against risks to property, such as fire, theft or weather damage. This includes specialized forms of insurance such as fire insurance, flood insurance, earthquake insurance, home insurance, inland marine insurance or boiler insurance.
Automobile insurance, known in the UK as motor insurance, is probably the most common form of insurance and may cover both legal liability claims against the driver and loss of or damage to the insured's vehicle itself.
C. credit insurance
Credit insurance repays some or all of a loan back when certain things happen to the borrower such as unemployment, disability, or death. Mortgage insurance is a form of credit insurance, although the name credit insurance more often is used to refer to policies that cover other kinds of debt.Mortgage insurance insures the lender against default by the borrower.
what else types of insurance can you figure out?