ABOUT INDIAN POPULATION

3.  A population is a summation of all the organisms of the
same group or species, who live in the same geographical
area, and have the capability of interbreeding.[1][2] In
ecology the population of a certain species in a certain
area is estimated using the Lincoln Index. The area that
is used to define a sexual population is defined as the
area where inter-breeding is potentially possible between
any pair within the area. The probability of interbreeding
is greater than the probability of cross-breeding with
individuals from other areas. Under normal
conditions, breeding is substantially more common
within the area than across the border.[3]

4.  The demographics of India are inclusive of the second
most populous country in the world, with over 1.21 billion
people (2011 census), more than a sixth of the world's
population. Already containing 17.5% of the world's
population, India is projected to be the world's most populous
country by 2025, surpassing China, its population reaching
1.6 billion by 2050.[4][5] Its population growth rate is
1.41%, ranking 102nd in the world in 2010.[6] Indian
population reached the billion mark in 2000.
 India has more than 50% of its population below the age of 25
and more than 65% below the age of 35. It is expected that, in
2020, the average age of an Indian will be 29 years, compared
to 37 for China and 48 for Japan; and, by
2030, India's dependency ratio should be just over 0.4.[7]

5.  : The average annual percent change in the
population, resulting from a surplus (or deficit) of
births over deaths and the balance of migrants
entering and leaving a country. The rate may be
positive or negative. The growth rate is a factor in
determining how great a burden would be imposed
on a country by the changing needs of its people for
infrastructure
(e.g., schools, hospitals, housing, roads), resources
(e.g., food, water, electricity), and jobs. Rapid
population growth can be seen as threatening by
neighboring countries.

6. 
A census is the procedure of systematically acquiring and recording information about
the members of a given population. It is a regularly occurring and official count of a
particular population. The term is used mostly in connection with national population
and housing censuses; other common censuses include agriculture, business, and traffic
censuses. The United Nations defines the essential features of population and housing
censuses as "individual enumeration, universality within a defined territory, simultaneity
and defined periodicity", and recommends that population censuses be taken at least
every 10 years. United Nations recommendations also cover census topics to be
collected, official definitions, classifications and other useful information to coordinate
international practice.