Here are some of the promises of his Hindu nationalist Bharatiya Janata Party (BJP), and analyst views on what could happen to them:
UNIFORM CIVIL CODE
The BJP's manifesto promised a national code to replace religion-specific civil laws in the country, a move many Muslims say is aimed at curbing centuries-old religious practices that the minority follows.
A uniform set of civil laws has been one of BJP's core promises but is communally contentious.
Indians from different religions follow laws specific to their faith or opt for a secular code. Laws on who and how many people a person can marry, how to end a marriage, and inheritance differ by religion. The new code will spell out the same set of rules for everyone.
The BJP says the code is critical to ensure gender justice, equality and to foster national unity and integration.
Analysts say plans for the code could be set aside in favour of bread and butter issues.
TEMPLES AT CONTROVERSIAL SITES
After Modi inaugurated a temple to the Hindu God Ram at a fiercely contested site earlier this year, fulfilling a long-held promise, some party leaders said in election rallies that another emphatic electoral victory would help them build temples on other disputed sites.
Hindu groups have long claimed that for centuries Muslim invaders built mosques over demolished Hindu temples. Courts are hearing cases against two such mosques in BJP-run Uttar Pradesh state: in Modi's Varanasi constituency and in Mathura.
Some BJP leaders have subsequently said there is no need to build temples in place of mosques without legal backing and stoke tensions, but existing Hindu religious sites could be developed to draw more tourists.
ONE NATION, ONE ELECTION
Modi's party has promised to implement an official report recommending elections to India's 28 state assemblies and national parliament at the same time, every five years.
Currently, state elections do not need to coincide with national elections, leading to a situation where the country hosts one election or another every few months.
A government-appointed panel in March said holding simultaneous elections would improve governance and growth, but Modi's opponents say it violates the federal system guaranteed in India's constitution.
The move will require a new law that will have to be passed by parliament and ratified by all states.
With the reduced margin - and protests from some opposition parties who fear the move could sideline smaller regional parties, help national parties dominate the narrative and create a presidential type of government - this move is unlikely to see the light of day for now.
"I think the Uniform Civil Code and the One Nation One Election will go on the back burner," said political analyst Rasheed Kidwai. "Modi was first among equals, which will now be challenged by his allies."
ECONOMY
The BJP manifesto says it aims to make India the third-largest economy in the world, from fifth-largest. The party promises to maintain high growth and low inflation while keeping budget deficit under control. It also talks about boosting manufacturing and creating employment opportunities, without giving details.
Experts say that Modi will have a tough balancing act in his third term as he will have to ensure that possible demands from key allies for welfare policies are met.
Analysts say Modi may also have to take supply-side measures like cuts in import duties to lower inflation as well as creating an environment for investments that lead to jobs - two key planks for the opposition during the election.
Amid a stronger opposition and to keep allies happy, Modi might also have to delay reforms attractive to investors such as labour laws that make it easier for companies to hire and fire, analysts said.
Political commentator Arati Jerath said there appeared to be a consensus in parliament around reform in general.
"But radical reforms like labour reforms, land reforms, I think the new government will have to go very slow on that," he said. "Because it's not just the pulls and pressures of the coalition government, but also a much stronger opposition."
In Modi's first term as prime minister, he tried to push through legislation that would have made it easier to buy land for industrial corridors, rural housing and electrification, and for defence purposes. However, the plan was put on hold amid stiff resistance from the opposition.
