Which one of the following is not a part of the Preamble of Indian Constitution?

The Preamble of the Indian Constitution is a formal enumeration of specific ideals that describe the nature of the Indian State and the objectives it secures for citizens. The Constitution (Forty-second Amendment) Act, 1976 inserted the words 'Socialist' and 'Secular' into the Preamble, so that India is now described as a Sovereign, Socialist, Secular, Democratic Republic, securing to all its citizens Justice, Liberty, Equality and Fraternity, and promoting the Unity and Integrity of the Nation. Only the ideals actually written into this text belong to the Preamble.

Checking each option against that fixed list: Socialism corresponds to the word 'Socialist' and Secularism corresponds to 'Secular' — both explicitly inserted into the Preamble by the 1976 amendment. Democratic corresponds to 'Democratic Republic', which has been part of the Preamble since its original 1950 text. Federalism, however, is nowhere written in the Preamble's text, in either version.

• Socialism — present as the word 'Socialist', added by the 1976 amendment.

• Democratic — present as 'Democratic Republic', part of the Preamble since its original 1950 adoption.

• Secularism — present as the word 'Secular', added by the 1976 amendment.

• Federalism — a structural feature of the Constitution: Article 1 describes India as a 'Union of States', and legislative powers are divided between the Union and the States under Article 246 read with the Seventh Schedule — but the word is never used in the Preamble's text, before or after 1976.

Cross-checking against the complete Preamble wording — Sovereign, Socialist, Secular, Democratic, Republic; Justice, Liberty, Equality, Fraternity; Unity and Integrity of the Nation — confirms that federalism is the one idea absent from this text, even though it independently describes India's constitutional structure.