Question

why is india called a sovereign country

Answer 1

 sovereign can be said "supreme" on its own power.
The word sovereign shows us that India is neither dependent or dominion of any other country but its own.
there is no one above it, it is free to take a decision for their own country ,free to decide on various global affairs

Answer 2

India is called a sovereign country because the Preamble of the Indian constitution defines India to be a ‘Sovereign’ country; meaning India has its own supreme law and not a matter of any additional state or nation. Moreover, India is independent of any kind of external intervention in its domestic operations. This notion can be found in the new system of nation-states. For instance, India is an active member of the United Nations Organization and the Commonwealth of Nations, despite, this cannot infringe on India's sovereignty.