Both Uses

demonstrate
in
Tuck Everlasting
(Edited)

You can show me where the spring is and help me to advertise. We'll set up demonstrations.
p. 98.4

demonstrations = displays (of how something works)
Once Winifred drinks some of the water, she'll do just as well for my demonstrations.
p. 100.3 *

Definitions:

(1) (demonstrate as in: It demonstrates my point.)
to show
The exact meaning of this sense of demonstrate can depend upon its context. For example:
- "I will demonstrate how to throw a Frisbee." -- show how to do something
- "I will demonstrate how much quicker the new computer is than the old one." -- show how something works
- "Her questioned demonstrated that she was listening and thinking deeply about what was said." -- showed to be true or proved
(2) (demonstrate as in: demonstrate to protest)
a public display supporting a cause -- usually joining with others in a political protest
(3) (meaning too rare to warrant focus)