Electoral systems translate votes cast into seats. They fall into three families: plurality-majority; semi-proportional; and proportional.
First-past-the-post, block vote, alternative vote, and the two-round system are plurality-majority systems.
The semi-proportional systems are parallel, limited vote (LV), and single non-transferable vote (SNTV).
List PR (proportional representation), mixed member proportional and single transferable vote are the proportional systems.
In first-past-the-post, the candidate with the most votes wins. In block vote, there are multi-member districts and voters have as many votes as there are seats. Alternative vote and two-round systems use second preferences if no one wins 50 percent in the first round.
In SNTV systems, each elector has one vote, but there are several district seats to be filled; candidates with the highest number of votes fill them. Parallel systems use both PR lists and plurality-majority districts. In LV systems there are multi-member districts, and winners are those who poll the most votes. Voters have fewer votes than there are seats to be filled, but more than one vote.
In proportional representation (PR) systems, a party that wins 40 percent of the votes wins approximately 40 percent of the seats. They may use party lists, a mixed system or preferential voting.