Definitions of demonstrate
to attend a public meeting or march where people show that they disagree with something or express views on a political issue by protesting, shouting and carrying signs etc
We want peace, we don't want war, and we will demonstrate and we will march until peace comes.
to show; to show that something is true by giving evidence or proof; to give a practical explanation as to how something works; to show or express something through the way that you act
The prosecutor needed to demonstrate that the accused wilfully killed others.