Final answer:
If a member of a parliament or state legislature dies or resigns, a by-election or special election is held to fill the vacancy. This is distinct from a general election which is scheduled at regular intervals. By-elections may operate under majority or plurality systems, depending on the country.
Step-by-step explanation:
If a member of a parliament or of a state legislature dies or resigns before completing their term, the election held to fill the vacant position is known as a by-election or a special election. This is not to be confused with a general election, which happens at regular intervals to select public office holders. By-elections can occur at any time during a term when a seat becomes vacant.
General elections comprise both majority and plurality systems. In a majority election system, a candidate must win more than 50% of the vote to be elected, possibly leading to a runoff if no single candidate achieves this threshold. In a plurality election system, the candidate with the most votes wins, regardless of whether they have a majority. By-elections may use either system, depending on the country's specific electoral laws.
For example, in the United States, if a senator leaves office before the end of their term, the governor sets a by-election to fill the vacancy. This is mandated by the 17th Amendment of the U.S. Constitution. Similarly, when a Member of Parliament (MP) in the United Kingdom passes away or resigns, a by-election is held to elect a new MP for the constituency.