Is it thumb a finger?
No, 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
No, Your thumb is different from your fingers. Your fingers have two joints and three bones called phalanges or phalanxes. A thumb only has one joint and two phalanges.
No, the thumb is a digit, but not technically a finger.
No, 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