An electoral system is defined as “the manner in which votes are translated into seats. Three key elements of any electoral system are:

• District size: the number of representatives elected in one electoral district;
• Electoral formula: by which the winner of a seat is chosen; and
• Ballot structure: which determines whether the voter votes for a candidate or a party, and whether the voter makes a single choice or expresses a series of preferences.[1]

There are three main electoral system families, classified according to how they translate votes into seats (plurality/majority, mixed and proportional systems) and a fourth family, into which individual systems that do not fit in the three main families are grouped. There are 12 individual electoral systems identified within these main families.[2]

• Plurality/majority systems are based on the principle that the candidate or party with a plurality of votes (i.e., more than any other) or a majority of votes (i.e., 50 per cent plus one—an absolute majority) is declared the winner. Such a system may use single-member districts (e.g., FPTP, alternative vote or the two-round system) or multi-member districts (e.g., block vote or party block vote).[1]
• Proportional representation (PR) is the electoral system family based on the principle of translating the overall votes of a party or grouping into a corresponding proportion of seats in an elected body. For example, a party that wins 30 per cent of the votes will receive approximately 30 per cent of the seats. All PR systems require the use of multi-member districts. There are two major types of PR systems: list PR and single transferable vote (STV).[2] 
• In a mixed system, voters’ choices are used to elect representatives using two different systems: one PR and one plurality/majority. There are two kinds of mixed systems: parallel systems and mixed-member proportional systems. As women’s representation on average is higher in PR systems than in plurality/majority systems, strategically designing a mixed system (for instance, electing half of the members of parliament through a PR system and the other half using a plurality/majority system) can be an effective way to increase women’s representation.[3] 
• Three types of individual electoral systems—single non-transferable vote (SNTV), limited vote (LV) and Borda count (BC)—form part of a fourth electoral system family, in which the SNTV system is a multi-member-district system in which voters can cast one vote for one candidate. LV is similar to the SNTV system, but voters have more than one vote (but less than the total number of candidates, as in the block vote system).”[4]