In voting systems, a voting system is monotonic if it satisfies the following condition:
- If an alternative X loses, and the ballots are changed only by placing X in lower positions, without changing the relative position of other candidates, then X must still lose.
The Borda count is monotonic, while Coombs' method and Instant-runoff voting are not. Approval voting is monotonic, using a slightly different definition, because it is not a preferential system: you can never help a candidate by not voting for them.
Some parts of this article are derived from text at http://condorcet.org/emr/criteria.shtml
Compare Monotonicity.