This glossary of social explains commonly used terms in social choice theory and political science relating to electoral systems, in alphabetical order. Some of these terms have their own pages, like plurality and proportional representation.
A
editabsolute majority
More than half of the total. It is a subset of a set consisting of more than half of the set's elements. A majority is different from, but often confused with, a plurality, which is a subset larger than any other subset but not necessarily more than half the set.
In social choice theory, an absolute majority
In parliamentary procedure, and common language the term absolute majority has different meanings.
acyclical
additional member system (United Kingdom)
The name of a two vote seat-linkage-based mixed electoral system used in the United Kingdom, a combination of first-preference plurality (on the winner-take-all tier) and closed list proportional representation (on the compensatory tier). Sometimes conflated with the term mixed-member proportional representation.
alternative
An element of the set from which a choice is to be made.
alternative vote
One of the names of the (first-preference) plurality-by-elimination single-winner system also known as instant-runoff voting, primarily in the United Kingdom.
at-large
An type of election or district where multiple winners are elected at once, with the same electoral method. Most commonly used in the context of winner-take-all electoral system and in the United States.
apportionment
Algorithm to determine how many seats are assigned to each electoral list.
approval ballot
A type of ballot where voters may approve (mark) or disapprove (not mark) each candidate, therefore they may approve of any number of candidates (even all or none). most commonly used for approval voting, whether single-winner or multi-winner. See also: single-choice ballot, ranked ballot, score ballot and cumulative ballot
approval voting (AV)
A single-winner cardinal voting system using approval ballots and the plurality rule. In a broader definition includes multi-winner systems using approval ballots, whether they use the plurality rule to determine winners or not.
A single winner electoral system electing the loser according to the plurality rule in a last-preference plurality system. Voters do not mark their first preference, only their last preference, and the winner is the alternative with the least amount of votes.
anti-plurality loser
The single winner of a last-preference plurality election. See
B
editballot
binary relation
binomial system (Chile)
Method to allocate seats in proportion to two separate characteristics, most commonly parties and regions.
block voting (BV)
block approval voting
bonus
Borda count
C
editcandidate
An alternative, when the subject of voting is electing people.
candidate method
cardinal system
choice set
choice function
An electoral list that remains unchanged by voting, where the ordering of candidates is pre-determined and voters have no direct influence on it. --- open list
Condorcet winner
Condorcet loser
Condorcet method
Condorcet paradox
cyclical
D
editdictator
dictatorship
divisor
double simultaneous vote (DSV)
A method of conducting multiple elections to separate offices – such as the president and members of a legislature – through a single vote, analogous to a single closed list election. The electoral methods used for the different elections may be different.
Droop quota
dual-member district
A type of multi-member district with two seats up for election (in each election). Some systems use exclusively dual-member districts, like the binomial system or dual-member mixed proportional.
E
editA set of rules used to determine the results of an election. Also known as a voting system.
elimination
exhaustive ballot
exhausted ballot
equality
equivalence relation
A symmetric quasi-ordering.
F
editfirst-past-the-post voting (FPTP)
Formally called first-preference plurality (FPP), a plurality rule voting system for electing a single winner, most commonly used with a single-choice ballot. The term is sometimes also applied to some forms of block voting.
first-preference plurality (FPP)
A more formal term for first-past-the-post voting, where only the first preferences of each voter are counted and the plurality rule decides the single winner of the election. May be used in single-member districts to elect multiple winners in a single election. FPP is formally a positional type of ranked voting method, however it does not require the use of ranked ballots, a ballot with a single mark is sufficient.
flexible list
see open list
free list
panachage or mixed list, is a variant on the most open list where voters may support candidates on different lists. Candidates are typically elected using either cumulative or block plurality voting. This gives the voters full control over which candidates are elected, not just within a particular party, but even across them.
fusion
Not to be confused with: electoral fusion, fusion voting
G
editgeneral ticket
H
edithistory dependence
I
editinstant runoff voting (IRV)
irrelevant alternative
J
editjackpot
L
editliberalism
list
largest remainder
M
editmajority
majority criterion
majority rule
median voter
method of equal shares
mixed ballot
mixed ballot transferable vote (MBTV)
mixed list
see free list
mixed-member system or mixed electoral system
mixed-member majoritarian (MMM) representation
mixed-member proportional (MMP) representation
Type of proportional representation that is achieved by mixed system: some seats are allocated by a winner-take-all method and some by a corrective mechanism. strict definition: the type of mixed electoral systems that provide proportional representation (requires a flexible amount of leveling seats). Broader definition: type of mixed electoral system with generally sufficient compensation to provide roughly proportional representation overall. Not all compensatory systems are mixed-member proportional. In New Zealand, a specific seat linkage system is referred to as MMP, in other countries, generic or specific proposals have also been labelled as MMP, regardless of them being striclty proportional.
mixed-member semi-proportional
mixed single vote (MSV)
monotonicity
multi-member district (MMD)
Electoral district with multiple seats elected at the same time (not staggered).
multiple non-transferable vote
limited (block) voting, block voting, limited (block) approval voting, block approval voting
multiple transferable vote
N
editnegative vote transfer
negative vote weight
A primary election in which all candidates for the same elected office run against each other at once, distinct from a two-round system and partisan primary.
O
editordering
---
A complete quasi-ordering.
ordinal voting
P
editA superposition method of mixed or hybrid electoral systems, where voters have two (independent) votes. Commonly conflated with mixed-member majoritarian representation. See superposition
pareto efficiency
participation criterion
partisan method
An electoral system officially incorporating political parties or other free associations, usually by use of electoral lists.
partisan primary
party-list method
Any voting system using electoral lists, whether proportional or not.
party block voting
pivotal voter
plurality winner
plurality loser
popular vote
positive vote transfer
preference
proportionality
Q
editquasi-ordering
A reflexive and transitive binary relation.
quasi-proportional
quasi-transitive
quota
R
editElectoral system where the election is decided on the basis of a single randomly-selected ballot.[1][2]
ranking
ranked voting
ranked-choice voting
remainder
runoff
runoff voting
S
editsemi-proportional representation
sincere voting
single-member plurality (SMP)
First-preference plurality (FPP) used exclusively in single-member districts (SMD). In practice single-choice ballots are used.
single non-transferable vote (SNTV)
single transferable vote (STV)
social choice
social choice theory
The mathematical analysis of collective decision making, the study of how individuals' preferences over certain alternatives can be aggregated into a social preference.
social welfare function
split-ticket
strategic voting
status quo
strict preference
superposition
supplementary vote
supplementary member system
symmetric
T
edittwo-round system (TRS)
two-round majority jackpot
top-up (seats): a form of compensation, typically in mixed electoral systems. Leveling seats, that are allocated in a separate (regionalized or at-large) district via seat linkage are usually referred to as top-up (vote linkage an non compensatory allocation is typically is not).
transferable vote
transitivity
U
editunanimity
unrestricted domain
utility
V
editvote
voter
vote transfer
W
editweak preference
winner
winner compensation
winner-take-all
- ^ Sewell, Roger; MacKay, David; McLean, Iain (January 2009). "Probabilistic electoral methods, representative probability, and maximum entropy". Voting Matters. 26: 22.
A voter is picked at random and the output ordering of the election is set to be the ordering given by that voter.
- ^ Zeckhauser, Richard (1973). "Voting Systems, Honest Preferences and Pareto Optimality". American Political Science Review. 67 (3): 938–940. doi:10.2307/1958635. ISSN 0003-0554. JSTOR 1958635. S2CID 147293110.
Each individual writes the name of a candidate on a ballot. The voters' ballots are collected and placed in a revolving drum. After shuffling, a ballot is chosen at random. The name on the chosen ballot is the elected candidate.