Article is the word used to refer to a section of a treaty, a written, legally-binding agreement between states.
Here is why Article 50 is important.
What is Article 50?
Article 50 of the Lisbon Treaty is the official method whereby Britain can start the process of leaving the EU.
The article states that any member state of the EU can leave the bloc “in accordance with its own constitutional requirements”.
That is, we can leave the EU according to our own laws.
So what actually happens?
Now that Britain has voted to leave the EU, Article 50 must be invoked. Britain must notify the European Council of its intention to leave and begin negotiations with other member states for its withdrawal.
After notifying the Council, Britain has a two-year window to complete negotiations over its terms of exit, unless a decision is made to extend the time period.
When will Article 50 be triggered?
It is up to Prime Minister David Cameron, or his replacement, to decide when to invoke Article 50.
Tory MP Liam Fox has called for a “period of calm” and reflection before starting the process. The architects of Britain’s EU departure believe it will take until 2020 to finalise the structure – including the relationship with the Single Union – under which Brexit will take place.
Is there any going back?
Nope. Once Article 50 is activated, the only way for Britain to re-enter the EU, through Article 49, is if all other member states give their consent.
Is Article 50 the only way to leave the EU?
There are differing opinions over this.
Kenneth Armstrong, a professor of European Law at the University of Cambridge, says Article 50 is the only legal way for Britain to leave the EU.
But Conservative MP Andrea Leadsom points out: “When Greenland left the EU article 50 didn’t exist.”
There are alternative methods for Britain to leave the bloc, through separate negotiations, she says.
“It’s perfectly possible to have a bilateral agreement with the European Union and to make different arrangements.”
Andrea Leadsom MP said: “So I think what we need to do is to calmly reflect on what the alternatives are but at the same time to look at the possibilities of a presumption of continuity for the free trade agreements that we are already party to as a member of the EU and all of the trade negotiations both with the EU and with other countries that at the moment we are unable to trade with directly.”