1. In anatomy, the thumb; also called, first finger, digitus 1, or digitus primus: If there were a contest of strength, the normal pollex would always be the winner over the other digits (fingers) of the hand.
2. The innermost digit of the forelimb of amphibians, reptiles, birds, and mammals: The pollex is the thumb of humans and other primates.
3. Having a skeleton of phalanges, joined by hinge-like joints that provide flexion toward the palm of the hand: The pollices have two phalanges (bones) instead of three, like the other digits or fingers.
4. Etymology: Latin pollic-, pollex or digitus primus, "thumb, big toe".

A backward deviation or abnormal variation of the position of the first big and large finger of the hand: Fern had a pollex extensus or thumb which was extended longer than normal.

The permanent flexion or bending of a joint of the thickest digit of each hand: Karl's pollex flaxus involved a deformity in the movements of the left thumb of his hand.

The abnormal deviation or slightly different position of the shortest and broadest finger toward the ulnar side (same side of the arm as the little finger) of the larger bone of the forearm: The pollex valgus indicated an unusual turning away of the thumbs from the palms of Susan's hands or toward the larger of the two long bones between the wrist and the elbow.

The abnormal turning of the thumb toward the radial (smaller bone) side of the forearm: Brandon's thickest and shortest fingers were abnormally positioned more towards the pollex varus or palms of his hands than is normal with most people.