monotonic sequence

A monotonic sequence is always increasing or always decreasing. Monotonicity does not imply uniform increasing (or decreasing) values. That is, the values may not be strictly sequential. While 1, 2, 3, 4 is a monotonic sequence, so is 4, 125, 291, 1424. 

Example usage: ServiceBusReceivedMessage.SequenceNumber Property

The sequence number is a unique 64-bit integer assigned to a message as it is accepted and stored by the broker and functions as its true identifier. For partitioned entities, the topmost 16 bits reflect the partition identifier. Sequence numbers monotonically increase. They roll over to 0 when the 48-64 bit range is exhausted.

That it can roll over means it's not strictly monotonic.

Monotonicity in election methods

Monotonicity is an election method criterion that requires the following:

Ranking or rating a candidate higher should never cause that candidate to lose, nor should ranking or rating a candidate lower ever cause that candidate to win, assuming all other candidates remain rated or ranked the same.

In other words, an election method is non-monotonic if either of the following is possible:

• A winner can be changed to a loser by experiencing an increase in support, OR
• A loser can be changed to a winner by experiencing a decrease in support.

One noteworthy non-monotonic election method is instant runoff voting (IRV).

source: https://electionscience.org/library/monotonicity/