The Parliament of the United Kingdom

ratification of the Treaty of Union Acts of Union passed by the Parliament of England (established 1215) and the Parliament of Scotland (c.1235), both Acts of Union stating, "That the United Kingdom of Great Britain be represented by one and the same Parliament to be styled The Parliament of Great Britain."
At the start of the 19th century, Parliament was further enlarged by Acts of Union ratified by the Parliament of Great Britain and the Parliament of Ireland (1297) that abolished the latter and added 100 Irish MPs and 32 Lords to the former to create the Parliament of the United Kingdom of Great Britain and Ireland.
The Government of Ireland Act 1920 created the parliaments of Northern Ireland Southern Ireland and reduced the representation of both parts at Westminster. The number of Northern Ireland seats was increased again after the introduction of direct rule in 1973.

The Irish Free State became independent in 1922, and in 1927 parliament was renamed the Parliament of the United Kingdom of Great Britain and Northern Ireland.

House of Lords,
and the House of Commons.
The Queen-in-Parliament (or, during the reign of a male monarch, King-in-Parliament), sometimes referred neutrally as the Crown-in-Parliament.
The Monarch also appoints the Prime Minister, who then forms a government from members of the Houses of Parliament.
No individual may be a member of both Houses, and members of the House of Lords are legally barred from voting in elections for members of the House of Commons.

consisting of 650 members known as members of Parliament (MPs). MPs are elected to represent constituencies by the first-past-the-post system and hold their seats until Parliament is dissolved. Although the House of Commons does not formally elect the prime minister, by convention and in practice, the prime minister is answerable to the House, and therefore must maintain its support.

Composition of Parliament

been approved by the House of Commons. It regularly reviews and amends bills from the Commons. While it is unable to prevent bills passing into law, except in certain limited circumstances, it can delay bills and force the Commons to reconsider their decisions. In this capacity, the House of Lords acts as a check on the more powerful House of Commons that is independent from the electoral process.

Composition of Parliament

"Aye!" and "No!" in the Commons—or "Content!" and "Not-Content!" in the Lords—and the presiding officer declares the result.
The pronouncement of either Speaker may be challenged, and a recorded vote (known as a division) demanded. (The Speaker of the House of Commons may choose to overrule a frivolous request for a division, but the Lord Speaker does not have that power.) In each House, a division requires members to file into one of the two lobbies alongside the Chamber; their names are recorded by clerks, and their votes are counted as they exit the lobbies to re-enter the Chamber.
The Speaker of the House of Commons is expected to be non-partisan, and does not cast a vote except in the case of a tie; the Lord Speaker, however, votes along with the other Lords.

Legislative procedure

the commencement of a session of the Parliament of the United Kingdom. It is held in the House of Lords. Before 2012, it took place in November or December, or, in a general election year, when the new Parliament first assembled. From 2012 onwards, the ceremony has taken place in May or June.
The monarch reads a speech, known as the Speech from the Throne, which is prepared by the Prime Minister and the Cabinet, outlining the Government's agenda for the coming year. The speech reflects the legislative agenda for which the Government intends to seek the agreement of both Houses of Parliament.

State Opening of Parliament