You have no room to talk about using the correct definition of a word! The correct term to refer to a person who has mental retardation is intellectual disability.
Always use person first language. Do not refer to someone as “that mentally retard person” or ” that autistic kid.” Put the individual firstif you have to mention their disability at all. Please remember that people who have disabilities are first and foremost people. They are not beneath you, do no refer to them strictly by their disability category.
Ex. ” The student with autism.” or “The student with intellectual disabilities.”
A handicap is a disadvantage placed upon a person with a disability by society. I.E. a sidewalk with no wheelchair access creates a handicap.
The use of handicap to refer to someone who has a disability is incorrect. The online dictionaries that define it as such were probably written by someone who has never taken a psychology class about exceptional students.
That parking space known as the “handicap spot” should really be the “parking spot reserved for persons who are disabled”.