Here are some examples:
* Mezzo-soprano: A female singing voice that is between soprano and alto.
* Mezzanine: A floor built between two main floors of a building, typically smaller and with a lower ceiling.
* Mezzotint: A type of printmaking technique that produces a soft, velvety effect.
* Mezzogiorno: A word meaning "midday" or "noon," specifically used in Italy to refer to the southern part of the country.
So, "mezzo" basically conveys the idea of something that's in between two extremes.