a public meeting or a march(= an organized walk by many people) at which people show that they are protesting against or supporting somebody/something

a demonstration(= an act of showing or explaining how something works or is done)

I'll give you a demo.

a version of an app or computer program that you can try out before you buy the full program

The full version costs £22.99, but there is a demo to try before you buy.

a recording of an example of somebody's music

The band have uploaded three demo tracks recorded last month.

a demographic(= a section of the population who are of a similar age, the same sex, etc.)

They're trying to appeal to a younger demo.

to use something, especially a piece of software, to show somebody or to see for yourself how it works

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