Final answer:
The term 'developmental disability' has been defined and redefined by acts such as the Rehabilitation Act of 1973, the Education for all Handicapped Children Act of 1975, and significantly by the Americans with Disabilities Act (ADA) of 1990, with later expansions in 2008.
Step-by-step explanation:
The term developmental disability is broadly defined by various acts over the years, with major contributions from the Rehabilitation Act of 1973 and the Education for all Handicapped Children Act of 1975, which was later renamed to Individuals with Disabilities Education Act (IDEA). The Americans with Disabilities Act (ADA) of 1990 further solidified the definition, moving away from the medical model and emphasizing the civil rights aspect by defining disability as a physical or mental impairment that substantially limits one or more major life activities. Additionally, in 2008, President Bush signed legislation that expanded the ADA's definition to cover more physical and mental impairments, making it easier for workers to challenge discrimination.