Geographical segregation exists whenever the proportions of population rates of two or more population

Population

A population is all the organisms that both belong to the same group or species and live in the same geographical area. The area that is used to define a sexual population is such that inter-breeding is possible between any pair within the area and more probable than cross-breeding with individuals...

s are not homogenous throughout a defined space. Populations can be considered any plant or animal species

Species

In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...

, human gender

Gender

Gender is a range of characteristics used to distinguish between males and females, particularly in the cases of men and women and the masculine and feminine attributes assigned to them. Depending on the context, the discriminating characteristics vary from sex to social role to gender identity...

s, followers of a certain religion

Religion

Religion is a collection of cultural systems, belief systems, and worldviews that establishes symbols that relate humanity to spirituality and, sometimes, to moral values. Many religions have narratives, symbols, traditions and sacred histories that are intended to give meaning to life or to...

, people of different nationalities, stone types, ethnic group

Ethnic group

An ethnic group is a group of people whose members identify with each other, through a common heritage, often consisting of a common language, a common culture and/or an ideology that stresses common ancestry or endogamy...

s, etc.

In social geography

Social geography

Social geography is the branch of human geography that is most closely related to social theory in general and sociology in particular, dealing with the relation of social phenomena and its spatial components. Though the term itself has a tradition of more than 100 years, there is no consensus on...

 segregation of ethnic group

Ethnic group

An ethnic group is a group of people whose members identify with each other, through a common heritage, often consisting of a common language, a common culture and/or an ideology that stresses common ancestry or endogamy...

s, social class

Social class

Social classes are economic or cultural arrangements of groups in society. Class is an essential object of analysis for sociologists, political scientists, economists, anthropologists and social historians. In the social sciences, social class is often discussed in terms of 'social stratification'...

es and genders is often measured by the calculation of indices such as the index of dissimilarity

Index of dissimilarity

The index of dissimilarity is a demographic measure of the evenness with which two groups are distributed across the component geographic areas that make up a larger area...

. Different dimensions of segregation (or its contrary) are recognised: exposure, evenness, clustering, concentration, centralisation, etc..