But for the very clear picture of this conclusion first of all we have to know that what is the federal constitution and what is unitary constitution.What feature of Indian constitution makes it federal or what features makes it unitary.
In this system the central government and the governments of the units act within a well defined sphere, co-ordinate and at the same time act independently. Wheare defines federal government as an association of states, which has been formed for certain common purposes, but in which the member states retain a large measure of their original independence.
A unitary system is governed constitutionally as one single unit, with one constitutionally created legislature. A unitary state is a sovereign state governed as one single unit in which the central government is supreme and any administrative divisions (sub national units) exercise only powers that the central government chooses to delegate.
This is one of the federal features of the Indian constitution.
The federal polity, in other words, provides a constitutional device for bringing unity in diversity and for the achievement of common national goals. A federal government exists when the powers of the government for a community are divided substantially according to a principle that there is a single independent authority for the whole area in respect of some matters and there are independent regional authorities for other matters, each set of authorities being co-ordinate to and subordinate to the others within its own sphere.
The Constitution of India has adopted federal features; though it does not, in fact, claim that it establishes a federation.