Here are some examples:
* Monotone: A single tone or pitch.
* Mononucleosis: A disease caused by a single type of virus.
* Monopoly: Exclusive control of a commodity or service.
* Monorail: A railway system with a single rail.
* Monotheism: The belief in a single God.
It can also be used to indicate something that is composed of only one element or type:
* Monosaccharide: A simple sugar made up of only one sugar unit.
* Monomer: A molecule that can be bonded to other identical molecules to form a polymer.