Final answer:
Abduction and adduction are the two motions at the shoulder joint that take place in the frontal plane, referring to movements of the limb away from and toward the body's midline, respectively.
Step-by-step explanation:
The two shoulder joint motions that occur in the frontal or coronal plane are abduction and adduction. Abduction is the motion of moving the limb or hand laterally away from the body, or spreading the fingers or toes, effectively moving them away from the midline of the body. Conversely, adduction is the movement that brings the limb, hand, or fingers toward or even across the body's midline, or brings the fingers or toes together. Both of these movements are crucial for various activities that involve upper limb mobility and coordination, such as lifting the arms to the side or bringing them together in front of the body.
Rotation, however, is a separate motion which involves turning of the upper limb at the shoulder, causing the anterior part of the limb to face either towards the midline of the body (medial or internal rotation) or away from the midline (lateral or external rotation), which occurs in the transverse plane.