Dictionary.com
definitions

monotonic

[mon-uh-ton-ik]
adjective
  1. of, relating to, or uttered in a monotone: a monotonic delivery of a lecture.
  2. Mathematics.
    1. (of a function or of a particular set of values of a function) increasing or decreasing.
    2. (of an ordered system of sets) consisting of sets such that each set contains the preceding set or such that each set is contained in the preceding set.

Origin of monotonic

First recorded in 1790–1800; monotone + -ic
Related formsmon·o·ton·i·cal·ly, adverb
Can be confusedmonotonic monotonous
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018