Approval Voting: A voting system where voters can select multiple candidates they approve of, with the candidate receiving the most approvals winning.
Arrow’s Impossibility Theorem: A mathematical theorem that states no voting system can satisfy a specific set of criteria, including the Condorcet and monotonicity criteria, when there are three or more candidates.
Ballot Exhaustion: Occurs when a voter’s ballot has no more ranked choices, so it is no longer considered in the vote tallying process.
Condorcet Criterion: The principle that an electoral system should always elect the Condorcet Winner if one exists.
Condorcet Winner: A candidate who would win a head-to-head contest against every other candidate in an election.
Duverger’s Law: A political science principle suggesting that single-member district plurality systems, like FPTP, tend to favor a two-party system.
Election Threshold: A minimum percentage of votes that a party or candidate must receive to be eligible for representation in a legislature.
Electoral Reform: The process of changing or improving electoral systems or voting processes.
First-past-the-post (FPTP): An electoral system where the candidate with the most votes wins, regardless of whether they have a majority.
Gerrymandering: The practice of manipulating electoral district boundaries to favor one political party or group, often resulting in distorted representation.
Instant Runoff Voting (IRV): Another term for Ranked Choice Voting, emphasizing that the voting process eliminates the need for separate runoff elections.
Majority: When a candidate receives more than 50% of the total votes cast.
Monotonicity Criterion: The principle that an electoral system should not allow a candidate to lose by gaining votes or win by losing votes.
Plurality: The highest number of votes received by a candidate, which may be less than a majority.
Preference Schedule: A table or diagram showing the preferences of each voter in an election, often used to illustrate RCV or other preference-based voting systems.
Proportional Representation: An electoral system designed to allocate seats in a legislative body in proportion to the number of votes each party or candidate receives.
Ranked Choice Voting (RCV): An electoral system in which voters rank candidates in order of preference instead of choosing just one candidate.
Simplicity Criterion: The principle that an electoral system should be easy for voters to understand and for election officials to administer.
Single Transferable Vote (STV): A proportional representation version of RCV, where multiple candidates are elected from a single district, and voters rank candidates in order of preference.
Spoiler Effect: A phenomenon in which a third-party or independent candidate’s presence in an election draws votes away from a major party candidate, potentially changing the election outcome.
Tactical Voting: When voters cast their ballots based on the perceived electability of candidates, rather than their true preferences.
Top-two Primary: A primary election in which the two candidates with the most votes, regardless of party affiliation, advance to the general election.
Two-round System: An electoral system in which a second round of voting is held if no candidate achieves a majority in the first round.
Voter Turnout: The percentage of eligible voters who cast a ballot in an election.
Vote Splitting: When two or more similar candidates divide the votes of a particular group, reducing their overall electoral impact.
AV: Approval Voting
BES: Ballot Exhaustion Syndrome
CG: Condorcet Guarantee
CC: Condorcet Criterion
CW: Condorcet Winner
DL: Duverger’s Law
ET: Election Threshold
IRV: Instant Runoff Voting
MC: Monotonicity Criterion
PS: Preference Schedule
PR: Proportional Representation
RCV: Ranked Choice Voting
SC: Simplicity Criterion
SE: Spoiler Effect
STV: Single Transferable Vote
TV: Tactical Voting
TTP: Top-two Primary
TRS: Two-round System