Mass. Gen. Laws ch. 176C § 1
In this chapter the following words and phrases shall have the following meanings:
"Medical service plan", any plan or arrangement whereby members of the public pay regular subscription amounts and are entitled in return therefor to medical services.
"Medical service corporation", any non-profit corporation which receives subscription payments from subscribing members and in return therefor makes available to subscribing members the benefits of any agreements which the corporation has with a medical organization for the rendering of care to its members.
"Medical organization", any medical society or partnership of physicians whose members are members of the Massachusetts Medical Society or other recognized association of physicians, or whose members are members of the staff of any hospital approved by the American College of Surgeons, and which agrees to provide medical services to the subscribing members of a medical service plan.
"Associated physician", any physician duly licensed to practice medicine in the commonwealth who complies with the qualifications, rules and regulations of a medical organization approved by the department of public health or any chiropractor registered under the provisions of chapter one hundred and twelve and who agrees in writing with the medical organization to perform any of the medical services specified in the form of subscribing members' agreement issued by a medical service corporation, and who agrees to accept compensation therefor in the manner hereinafter set forth.
"Recognized association of physicians", an organized medical society or association, membership in which is contingent upon established professional qualifications and which is nationally recognized in the medical profession.
"Subscribing member", any member of the public who is accepted as a subscribing member, with or without dependents, by a medical service corporation and who pays regular subscription dues to such corporation.
Mass. Gen. Laws ch. 176C, § 1