If the UK left the EU, would it be able to rejoin in the future?
A few people have asked this question - and the answer is yes. BBC Europe editor Katya Adler says the UK would have to start from scratch with no rebate, and enter in to accession talks with the EU. Every member state would have to agree to the UK re-joining. But she says with elections looming elsewhere in Europe, other leaders might not be generous towards any UK demands.
The mechanisms for re-joining the EU are set out in the Lisbon Treaty. According to Article 50: "If a state which has withdrawn from the Union asks to rejoin, its request shall be subject to the procedure referred to in Article 49."
And Article 49 states: "The applicant state shall address its application to the Council, which shall act unanimously after consulting the Commission and after receiving the assent of the European Parliament, which shall act by an absolute majority of its component members. The conditions of admission and the adjustments to the Treaties on which the Union is founded, which such admission entails, shall be the subject of an agreement between the member states and the applicant state."
New members are required to adopt the euro as their currency, once they meet the relevant criteria, although the UK could try to negotiate an opt-out.