It is difficult to exactly define a tribe. There have been various categorisations put forward over the decades but due to the ever changing nature of the tribal people as well as differing levels of integration and assimilation among different tribes, these definitions fail to apply generically.

The criteria given by some anthropologists is that a tribe is a group which a competent anthropologist considers a tribe. The government of India follows in this vein and only those groups mentioned in the schedule list are considered as tribes for the purpose of affirmative action. A competent anthropologist may still consider a group, not mentioned in the schedule, as a tribe for the purposes of a study.

DN Majumdar defines a tribe as a social group with:

• Territorial affiliation,
• United in language or dialect,
• Endogamous,
• With no specialisation of functions,
• Ruled by tribal officers, hereditary or otherwise,
• Recognising social distance with other tribes or castes without any social stigma,
• Following tribal traditions, beliefs and customs,
• Illiberal to naturalisation of ideas from alien sources,
• Conscious of ethnic homogeneity and territorial integration.

The definitional problems arise because exceptions (in large numbers) can be found to almost all of these criteria of defining a tribe.

Tribal societies are often marked by social differentiation rather than stratification. However, increasing cultural contact with caste society has introduced elements of stratification as well. These societies are differentiated on the basis of:

1. By kin group and descent.
2. By sex
3. By age
4. By rank
5. By occupation
6. By education
7. By religion
8. By language

George Ritzer says differentiation as a social process that is a precursor to stratification. Differentiation is a hierarchical system in which inherited or personal differences come to be the basis for fulfilling social roles and positions.

Tribes undergoing changes in stratification caused by:

1. Political reservations. Leaders are more concerned with tribal elites than the adivasi. G. Shah
2. Modernisation and government schemes for upliftment are being taken up differently.
3. Sanskritisation of tribes.
4. Ethnic differences.

Tribes are relatively isolated from larger cultural influences, have a relative cultural homogeneity and a simple technology. They believe in spirits, magic and witchcraft. They have their own taboos which prohibit certain actions that are punishable by the community, by the supernatural, or by magical consequences. Large number of the tribes believes in animism, according to which all objects counselled – both animate and inanimate – are permanently or temporarily inhabited by spirits or souls. Often, an activity is believed to be caused by these spirits. Some spirits are worshipped and treated with fear and respect. Some scholars have maintained that animism was the earliest form of religion of the tribes. Many tribes believe in ancestor worship too.

Some general defining features of tribes in India are :

• Common name: Each tribe has a distinct name of its own through which it is distinguished from others.
• Common territory: Tribes generally occupy common geographical areas.
• Common language: Members of one tribe speak the same language. Each tribe has its own dialect, if not the script.
• Common culture: Each tribe has prescribed patterns of behaviour and festivals and deities to worship.
• Endogamy: Each tribe has the practice of marrying members within their own tribe.
• Political organization: All tribes have their own political organization. They have councils of elders to control members.