Britain's unpredictable election is steeped in the rich — and sometimes confusing — lexicon of parliamentary democracy. Some key terms:

FIRST PAST THE POST: Used to describe the electoral system, in which voters across the country elect local Members of Parliament. The candidate with the highest number of votes in each area wins, even if he or she does not gain a majority of votes cast.

HUNG PARLIAMENT: The probable outcome of Thursday's vote. A hung parliament, the equivalent of a hung jury, is one in which no single party holds a majority of the 650 seats in the House of Commons. In that case, parties will try to forge agreements that will assemble a working majority enabling a government to pass laws.

COALITION GOVERNMENT: Once a rarity in Britain, a government in which two or more political parties divide up ministerial posts, compromise on policies and agree to govern in concert. The Conservative-Liberal Democrat coalition assembled in 2010 was Britain's first since World War II.

MAJORITY/MINORITY GOVERNMENT: A majority government is formed by a party that holds more than half the seats in the House of Commons. Minority government occurs when a party that does not have a majority of seats governs alone, relying on support from smaller parties on a vote-by-vote basis. Britain last had minority governments in the 1970s, and they tended to be short-lived.

NO-CONFIDENCE MOTION: British governments draw their authority from Parliament, and lawmakers can topple a government by passing a motion stating "that this House has no confidence in Her Majesty's Government." If the government can't win an opposite motion expressing confidence within 14 days, a new election is called.

CONFIDENCE AND SUPPLY AGREEMENT: One or more parties agrees to support the government on votes crucial to its survival: no-confidence motions and spending (or supply) votes.

QUEEN'S SPEECH: An annual speech, read by the monarch at the ceremonial State Opening of Parliament, the Queen's Speech is written by the government and outlines its legislative program. Winning the vote that follows is crucial to the survival of any government. This year's Queen's Speech will be May 27, when either Conservative leader David Cameron or Labour's Ed Miliband will unveil his government's plans.