"monotone" in the noun sense
1. monotone, drone, droning
an unchanging intonation
2. monotone
a single tone repeated with different words or different rhythms (especially in rendering liturgical texts)
"monotone" in the adjective sense
1. monotonic, monotone
of a sequence or function consistently increasing and never decreasing or consistently decreasing and never increasing in value
2. flat, monotone, monotonic, monotonous
sounded or spoken in a tone unvarying in pitch
"the owl's faint monotonous hooting"
Source: WordNet® (An amazing lexical database of English)
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