Eugenics refers to the study of hereditary improvement by genetic control; a science, based on the principle of heredity, that has for its purpose the improvement of the race.
Eugenics is also a social philosophy that advocates the improvement of human hereditary traits through various forms of intervention. At the end of the 19th century, Eugenicists believed disabled people would weaken the gene pool and reduce competitiveness. Increasingly, disabled people were sterilised or shut away in single sex institutions for life. Separate special schools and day-centres were set up that denied non-disabled people the day-to-day experience of living and growing up with disabled people, and vice-versa. Moreover, Eugenics is also defined as the use of selective breeding to increase the general intelligence of the population; an effort to improve the human species by letting only people whose characteristics are valued by a society mate and pass along their genes.
Other /More definition:
eugenics first defined by Sir Francis Galton in 1883 as "the science which deals with all influences that improve the inborn qualities of a race.” In the early 1900s, public and professional emphasis shift ed away from the needs of persons with mental retardation toward a consideration of the needs of society; society was to be protected from the presumable harm done by the presence of these persons in the community. This misdirected view provided justification for restricting the rights of individuals with mental retardation and their opportunities for advancement.