Prime Minister of India
The Prime Minister of India is the leader of the executive of the Government of India. The prime minister is also the chief adviser to the President of India and head of the Council of Ministers. They can be a member of any of the two houses of the Parliament of India—the Lok Sabha (House of the People) and the Rajya Sabha (Council of the States)—but has to be a member of the political party or coalition, having a majority in the Lok Sabha.
Leader of the Opposition (India)
While the position also existed in former Central Legislative Assembly of British India, and holders of it there included Motilal Nehru, it received statutory recognition through the "Salary and Allowances of Leaders of Opposition in Parliament Act, 1977" which defines the term "Leader of the Opposition" as that member of the Lok Sabha or the Rajya Sabha who, for the time being, is the Leader of that House of the Party in Opposition to the Government having the greatest numerical strength and recognised, as such, by the Chairman of the Rajya Sabha or the Speaker of the Lok Sabha. However, in order to get formal recognition, the concerned party must have at least 10% of the total strength of the House (55 seats in the Lok Sabha). If any party fails to get 10% seats in opposition, the House will not have recognised leader of the opposition. A single party has to meet the 10% seat criterion, not an alliance.