General Usage:
* Democracy: A system of government where supreme power is vested in the people and exercised by them directly or indirectly through a system of representation, usually involving periodically held free elections.
* Demographics: Statistical data relating to the population and particular groups within it.
* Endemic: Native or confined to a particular region or people.
* Pandemic: Prevalent over a whole country or the world.
* Epidemic: A widespread occurrence of an infectious disease in a community at a particular time.
* Demagogue: A political leader who seeks support by appealing to the desires and prejudices of ordinary people rather than by using rational argument.
* Demography: The study of statistics such as births, deaths, income, or the incidence of disease, which illustrate the changing structure of human populations.
* Demographic: Relating to the structure of populations.
* Demos: (archaic) The common people.
More Specific Usage:
* Demolition: The act of destroying a building or other structure.
* Demolish: To destroy completely.
* Demolitionist: One who advocates for the destruction of something.
* Demophobia: Fear of crowds or large groups of people.
* Demospongiae: (Biology) Class of sponges with siliceous spicules and a skeleton of spongin.
Note: "Demo" can also be a shortened form of "demonstration," as in a "demo day" for a startup company.
This is not an exhaustive list, but it gives you a good starting point for understanding how the Greek root "demo" influences the meaning of words.