Democracy, a small number of related forms of government

Demography, the statistical study of human populations

Software prototyping, in particular; release of prototype versions of in-progress software

Demolition, the tearing-down of buildings and other structures

Demo (computer programming), a non-interactive multimedia presentation, a type of digital art

Demoscene, collectively, the digital artists who create demos

Democide, the murder of any person or people by a government

An alternate term for an exhibition game in sports

DEMO, a proposed experimental nuclear fusion reactor

Game demo, more narrowly; a freely-distributed "try-out" version of a video game, usually fully playable but incomplete

Performance of a demonstration sport

Demo (techno group) (демо), a Russian techno music group

Demo (music), a song recorded for reference rather than release

Demo (comics), a comic book series by Brian Wood and Becky Cloonan

Demoware, software that users can test in a limited fashion before buying

Technology demo, a prototype version of a technology product, to showcase its forthcoming ideas, performance, method or features

Demo mode, a feature often found in consumer electronics, which shows the owner the features of the machine

Demo (company), a co-developer of the ZSNES Super Nintendo emulator and the ePSXe PlayStation emulator