Thumb facts for kids
The thumb is one of the five fingers on the human hand. Thumbs are different from the other four fingers because they are in a different direction, have only 2 bones (the others have 3), and are shorter. Thumbs allow us to pick things up. This is called having "opposable thumbs". Thumbs have an artery in them. Arteries have a pulse. This is why we should not take other peoples' pulses with our thumbs.
Images for kids
A bonobo "fishing" for termites, an example of incomplete/"untrue" opposition.
Thumb Facts for Kids. Kiddle Encyclopedia.