INDIA: UNION OF STATES
Article 1 of the Indian Constitution describes India i.e. Bharat as a Union of States and not a Federation of States. Dr. Bhim Rao Ambedkar in the debate of Constituent Assembly had explained the difference between a Federation and a Union while justifying India as Union of States. He explained, that USA came into existence by the agreement among the northern and southern states States of USA i.e. here American states by coming together through a compact or agreement created a country. Therefore, USA is example of a Federation. In a Federation a State has right to secede from the Federation. Because of this right, American States had to wage a Civil War for keeping all US States under the Federation as some of the US constituent states wanted to secede from the Federation.
But in the case of India, it is just reverse. After freedom from the British Rule, India came to existence first as a nation and later all the states were created for administrative convenience. By taking example of American Civil War, it was clarified in the Constituent Assembly by Dr. Ambedkar that since India is not a result of agreement among its constituent states and neither any state has right to secede, therefore, India shall be called as " UNION OF STATES".