demonstrator
🇺🇸
/ˈdemənstreɪtər/
🇬🇧
/ˈdemənstreɪtə(r)/
A person who publicly shows support or protest for a cause.
The soldiers clashed with the demonstrators in the city square.
A person who shows how to use a product or perform a task.
The demonstrator showed us how to use the new software.