Why India is declared as a …

In India both the state and the central governments derive their authority from the constitution. But India is a federation with unitary features. This is because :

• Central government makes laws on the subjects included in the Union List while states make laws on the subjects in the state list. Both governments can make laws in the concurrent list. But in the case of disputes between the two governments, the will of the central government prevails.
• The constitution has empowered the central government to make a change in the boundaries of the states.
• States do not have the right to form their own constitution unlike in the USA  where states can form their own laws.
• In India, people are the citizens of their country. They have single citizenship. They are not the citizens of their states unlike in the USA. 
• The state government in India is elelected  by the people. But if the union government feels that the state government is breaching the constitution, it can declare a constitutional emergency in the state where by the state government can be dismissed.