Turkish people are heading to the polls to decide whether their parliamentary system should change to a presidential one.
What is the referendum about?
Turkish citizens will vote on whether to change their constitution which was adopted in 1982.
There are 18 proposed amendments but the most significant proposes to transition from a parliamentary to a presidential system. This would mean scrapping the position of prime minister. The presidency would change from a ceremonial position to an executive position.
The age of eligibility for lawmakers would also change from 25 to 18, and the number of parliamentarians would rise from 550 to 600. The president would have the power to appoint cabinet ministers and senior judges.
If passed, the amendments would also see presidential and parliamentary elections held at the same time every five years.
Who are the main parties and what do they want?
There are four main political parties in this referendum and they have formed two broad camps.
The ruling AK Party (Justice and Development Party) and MHP (Nationalist Movement Party) are campaigning in favour of "yes." They argue that a presidential system will bring about political stability and it will allow for a democratic transition of power.
How does it work?
Turks over the age of 18, in 81 cities across the country are eligible to vote.
Citizens living abroad have been able to vote from March 27 until April 9. Voting stations have been set up at 120 diplomatic missions in 57 countries. Ballot boxes have also been placed at six Turkish border posts and at some airports.
When does it take place?
Sunday, March 16 is voting day.
Polling stations will open at 8am and close at 5pm in the west regions and from 7am to 4pm in Turkey's eastern provinces. Results will start coming in later that night.
What is the voting process?
Voters can only cast their ballots in the areas where they live.
Ballots are white and brown with "evet" which means yes on the white side and "hayir", no, on the brown side. Votes are cast and then slipped into a transparent ballot box.
Polling stations have been set up at schools across the country, and state employees such as teachers run the voting centres.
Each political party sends a representative to monitor the counting process and make sure it is fair and correct.
The Supreme Election Council will conduct the referendum while organisations like Oy Ve Otesi - a civilian volunteer initiative will oversee the ballot to ensure that it is free and fair.
What does a "yes" vote mean?
Not all of the constitutional amendments would take effect immediately.
The Office of the Prime Ministry will not be scrapped until November 2019 when parliamentary and presidential elections take place.
President Erdogan will at once able to rejoin the AK Party as any constitutional obstacles to a president affiliated with a political party will be removed.
The president will appoint one or more vice presidents.
"It will be a cumbersome and a long process that will take years to adjust, so in a sense, a 'yes' vote will mean the start of a process that will take more than a year to finish," Al Sharq Forum's Research Director, Galip Dalay told TRT World.
What does a "no" vote mean?
The system would remain the way that it is.
The government will be bound by the outcome of the referendum but a no-vote would create some political uncertainty.
"It would lead to a situation of ambiguity in the political domain, which could push Turkey to an atmosphere of early elections," the Foundation for Political, Economic and Social Researcher's Can Acun told TRT World.
Al Sharq's Dalay, who specialises in Turkey and Kurdish affairs said it would send a strong message to Turkey's ruling party.
"To some extent it would deal the first blow to the AK party in quite some time. We will probably see some soul-searching within the AK Party. Turkey probably will have a short-term political uncertainty, but, nevertheless, it will depend on what kind of measures and what kind of steps that the governing party and the president will take."
Are the results legally binding?
Yes, irrespective of the outcome.
For constitutional reform to go to a referendum, a proposal must first go through parliament. If the proposal receives between 330 to 367 votes from MPs in parliament, the president could either send the reforms back to parliament to be debated or put the question to the public in the form of a referendum.