A TD or Teachta Dála (pronounced 'chock-ta dawla') is the Gaelic version for MP (Member of Parliament) used to describe members of Dáil Éireann, the lower chamber of the Irish Oireachtas (pronounced 'orr-och-tas').
The term was first used to describe those Irish MPs elected in the 1918 general election from the island of Ireland who instead of attending the Westminster House of Commons, to which they had been elected, assembled instead in Dublin to create a new Irish parliament, Dáil Éireann. The initials T.D. are placed after the surname of the TD elected. For example, the current Irish Taoiseach (prime minister) is referred to as 'Bertie Ahern, T.D.' Whereas many parliamentarians are addressed using certain styles (e.g., 'Honourable', 'Right Honourable', etc.), no style is used to address members of Dáil Éireann.
The initials TD have been used to refer to members of every Irish parliament since that First Dáil assembled in 1919. It was used to refer to members of the Irish Republic's single chamber Dáil Éireann (translated as the 'Assembly of Ireland') (1919-1922), members of Dáil Éireann (translated as 'Chamber of Deputies') during the Irish Free State (1922-1937) and the Dáil Éireann (translated as the 'House of Representatives') of Éire (1937-present) and the Republic of Ireland.
(See Dáil Éireann for additional information on the election system and current composition of the house.)