1) Decreasing monotonic 2) Increasing monotonic 3) Monotone 4) Of a sequence or function 5) Unvarying in pitch 6) Uttered in a dull way 1) Monotone 2) Monotonous 3) One note 4) Unmelodic 
• (a.) Alt. of Monotonical
Changing in one direction only; thus either strictly rising or strictly falling, but not reversing direction.
The property of a function that is always strictly increasing or strictly decreasing, but never both.
The property of a function that is always strictly increasing or strictly decreasing, but never both. The sigmoidal activation function of a multilayer perceptron is monotonically increasing. 
[adj] - (mathematics) of a sequence or function
A DAC is said to be monotonic if the output increases as the digital input increases, with the result that the output is always a single valued function of the input
Designating sequences, the successive members of which either consistently increase or decrease but do not oscillate in relative value. Each member of a monotone increasing sequence is greater than or equal to the preceding member; each member of a monotone decreasing sequence is less than or equal to the preceding member. 
adjective of a sequence or function; consistently increasing and never decreasing or consistently decreasing and never increasing in value
of, pertaining to, or uttered in a monotone: a monotonic delivery of a lecture. · · (of a function or of a particular set of values of a function) increasing or decreasing. · (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.