Which of the following terms is expressly mentioned in the Preamble to the Constitution of India to delineate the character of the Indian State?

The correct answer is Democratic.

Explanation:
The Preamble to the Constitution of India solemnly resolves to constitute India into a "SOVEREIGN SOCIALIST SECULAR DEMOCRATIC REPUBLIC".

Let's evaluate the options provided:
1. Democratic: Expressly mentioned in the Preamble. It indicates that the authority of the government is derived from the people through democratic processes and elections.
2. Unitary: The term "Unitary" is nowhere mentioned in the Preamble or in the text of the Constitution of India.
3. Federal: The word "Federal" is not mentioned in the Preamble. Article 1 of the Constitution describes India as a "Union of States," even though the structure contains federal characteristics.
4. Parliamentary: Although India operates under a parliamentary system of governance, the word "Parliamentary" is not explicitly stated in the Preamble.

Therefore, Democratic is the term explicitly mentioned in the Preamble to describe the character of the Indian State.