Here are some examples of how it's used:
* Monopoly: A situation where one company or person has complete control over a particular industry or market.
* Monotone: A single, unchanging tone of voice.
* Monorail: A train system that runs on a single rail.
* Monocle: A single eyeglass lens worn over one eye.
* Monotheism: The belief in one God.
Let me know if you have any other words with "mono" in them that you'd like to understand!