Monotone means speaking or making sound in a flat, unchanging tone, without any variation in pitch or emotion. When someone talks in a monotone voice, every word sounds the same: not higher, not lower, not excited, not sad, just one steady, unchanging note, like a robot reading a grocery list.

Imagine a teacher reading announcements over the loudspeaker in the exact same flat voice: “Today is pizza day. pause The library is closed. pause Congratulations to the chess team.” No excitement for pizza day, no disappointment about the library, just the same dull tone for everything. That's monotone.

Monotone can make even interesting subjects sound boring. A documentary narrator speaking in monotone might describe an erupting volcano or a thrilling rescue with the same flat voice they'd use to read a phone book. Our voices naturally rise and fall when we're interested or excited, so monotone can signal boredom, tiredness, or disinterest.

Less commonly, monotone can describe anything that's unchanging and dull, like the monotone beige walls of an old office building.