Explanation:

• A democratic polity can be classified into two categories—monarchy and republic.
• In a monarchy, the head of the state (usually king or queen) enjoys a hereditary position, that is, he comes into office through succession, e.g., Britain.
• In a republic, on the other hand, the head of the state is always elected directly or indirectly for a fixed period, e.g., USA.
• Therefore, the term ‘republic’ in our Preamble indicates that India has an elected head called the president.
• He is elected indirectly for a fixed period of five years.
• A republic also means two more things: one, vesting of political sovereignty in the people and not in a single individual like a king; second, the absence of any privileged class and hence all public offices being opened to every citizen without any discrimination.