monotonically increasing function

noun
UK /ˌmɒnəˈtɒnɪkli ɪnˈkriːsɪŋ ˈfʌŋkʃən/
US /ˌmɑːnəˈtɑːnɪkli ɪnˈkriːsɪŋ ˈfʌŋkʃən/

A function that never goes down as you move to the right.

The function f(x) = 2x is monotonically increasing because bigger inputs always give bigger outputs.


OTHER MEANINGS

2. A function whose output never decreases, though it may stay flat between points.

The step function that stays at 1 and then jumps to 2 is monotonically increasing.

3. A function where x1 < x2 always implies f(x1) ≤ f(x2).

We proved the sequence is monotonically increasing by checking each consecutive pair.

4. In some texts, a strictly increasing function where x1 < x2 implies f(x1) < f(x2).

Some authors call f(x) = x³ monotonically increasing in the strict sense.