The thumb contrasts with each of the other four by being the only digit that: Is opposable to the other four fingers. Has two phalanges rather than three. Has greater breadth in the distal phalanx than in the proximal phalanx.
Hereof, is the the thumb a finger?
It's therefore more accurate to describe a thumb as one of five digits that we have on each hand, rather than as a finger. 'Digit' is the technical term which covers fingers, thumbs, and toes in humans, and similar appendages in some animals. The thumb is the short, thick first digit of the human hand.
What is unique about human hands?
What makes human hands unique? The human opposable thumb is longer, compared to finger length, than any other primate thumb. This long thumb and its ability to easily touch the other fingers allow humans to firmly grasp and manipulate objects of many different shapes.
Why do they call it a thumb?
Because the human thumb is different from the other fingers as it is opposable (which allows us to grab hold of objects with our thumbs on the opposite side of the object to the other fingers) whereas the big toe is not opposable and is simply bigger than the other toes.