The Scheduled Castes (SCs) and Scheduled Tribes (STs) are various officially designated groups of historically disadvantaged people in India. The terms are recognised in the Constitution of India and the various groups are designated in one or other of the categories. For much of the period of British rule in the Indian subcontinent, they were known as the Depressed Classes. The combined percentage of people in scheduled castes and scheduled tribes is essentially the official percentage of people in the lowest part of Indian society.
In modern literature, the Scheduled Castes/Tribes are sometimes referred to as untouchables; in Tamil Nadu they are referred as Adi Dravida or Paraiyar; and in other states mostly referred as Dalits.
The Scheduled Castes and Scheduled Tribes comprise about 16.6 percent and 8.6 percent, respectively, of India's population (according to the 2011 census). The Constitution (Scheduled Castes) Order, 1950 lists 1,108 castes across 29 states in its First Schedule, and the Constitution (Scheduled Tribes) Order, 1950 lists 744 tribes across 22 states in its First Schedule.
Since independence, the Scheduled Castes and Scheduled Tribes were given Reservation status, guaranteeing political representation. The Constitution lays down the general principles of positive discrimination for SCs and STs.
Since the 1850s these communities were loosely referred to as Depressed Classes, with the Scheduled Tribes also being known as Adivasi ("original inhabitants"). The early 20th century saw a flurry of activity in the British authorities assessing the feasibility of responsible self-government for India. The Morley–Minto Reforms Report, Montagu–Chelmsford Reforms Report and the Simon Commission were several initiatives in this context. A highly contested issue in the proposed reforms was the reservation of seats for representation of the Depressed Classes in provincial and central legislatures.