1 [+ obj] a : to prove (something) by showing examples of it : to show evidence of (something) ▪ Each student must demonstrate mastery of the subject matter in order to pass the class. ▪ Employees must demonstrate competence in certain skills before they can work independently. ▪ The medication will not be marketed until it is demonstrated to be safe. b : to prove (something) by being an example of it : to be evidence of (something) ▪ The town's crowded classrooms demonstrate [=point to] the need for more schools in the area. ▪ The latest test results clearly demonstrate that the vaccine works. ▪ The group's failed efforts demonstrate how difficult it is to convince people to change their habits.
2 [+ obj] : to show (a quality, feeling, etc.) clearly to other people ▪ They have demonstrated a willingness to negotiate.
3 [+ obj] : to show or explain how something is used or done : to show or explain the function or use of (something) ▪ Several people will be demonstrating traditional farming techniques. ▪ The instructor demonstrated the correct procedure for pruning a tree. ▪ Would you mind demonstrating how the machine works?
4 [no obj] : to take part in an event in which people gather together in order to show that they support or oppose something or someone ▪ A large crowd was demonstrating [=protesting] downtown. ▪ Protesters demonstrated against the war.