Final answer:
The joint connecting the hand to the forearm is the wrist joint, formed by the articulation of the radius and carpal bones. It provides versatile movement, notably in the thumb joint which can move in various directions.
Step-by-step explanation:
The joint where the hand is connected to the arm is called the wrist joint. This articulation involves the bones of the forearm (the radius and ulna) on one end, and the carpal bones of the wrist on the other. The hand itself is composed of these eight carpal bones, the five metacarpal bones of the palm, and the 14 phalanges of the fingers and thumb. Specifically, the radius, located on the lateral (thumb) side of the forearm, articulates with the carpal bones to form the wrist joint. The thumb joint, also known as the carpometacarpal joint, is particularly notable because it allows for versatile motion, such as back and forth and up and down movements.