Section 12A. For the purposes of sections twelve A to twelve C, inclusive, the following words shall have the following meanings:

''Disabled person'', a person who is unable to engage in substantial gainful activity by reason of medically determinable physical or mental impairment which can be expected to result in death or be of at least twelve months' duration; provided, however, that such impairment is of such severity that such individual is unable to do his previous work, if any, and, considering his age, education, and work experience, cannot engage in substantial gainful activity.

''Education authority'', the school committee or other education provider responsible for the provision of special education pursuant to the provisions of this chapter.

''Habilitative services'', services directed toward the alleviation of limitations on major life activities of a disabled person, including diagnosis, evaluation, treatment, personal care, daycare, respite care, home care, residential care, group care in a community residence, special living arrangements, training, education, sheltered employment, supported work, recreation, counseling, protective and social services, legal services, information and referral services, and transportation services.

''Major life activity'', self-care, including personal hygiene, dressing and eating; communication and language skills, including reception and expression; learning; mobility; capacity for independent living; and economic self-sufficiency.

''Substantial gainful activity'', the performance of a task for at least twenty hours per week for which a disabled person receives compensation either in currency or in-kind; provided, however, that such activity shall not include sheltered workshops, supported work, occupational therapy or any other work activity supported by the federal, state, or local governments for the purpose of assisting such disabled person to participate in such activity.

''Transitional plan'', a plan for a program of habilitative services for disabled person whose entitlement to services under special education programs has terminated or will terminate as a result of such person's graduation from high school or attainment of age twenty-two.