Sounded or spoken in a tone unvarying in pitch; SYN. monotonic, monotonous.

(Mathematics) Of a sequence or function; consistently increasing and never decreasing or consistently decreasing and never increasing in value; SYN. monotone.

ETYM Greek; monos alone, single + tonos tone. Related to Tone.
Tedious; continued with dull uniformity; characterized by monotony; without change or variety; wearisome.

In a monotonous manner.