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The teres major is not considered part of the rotator cuff, which is a group of four muscles that stabilize and support the shoulder joint. The muscles that make up the rotator cuff include the supraspinatus, infraspinatus, teres minor, and subscapularis.

The primary role of the rotator cuff muscles is to keep the head of the humerus firmly within the shallow socket of the scapula, providing essential stability during overhead and arm movements. The teres major, while it does contribute to shoulder movement, particularly in adduction and medial rotation, does not have the same stabilizing function necessary for the rotator cuff. Understanding this distinction is important for training and rehabilitation purposes, as it helps in identifying exercises that strengthen the stabilizers versus the primary movers of the shoulder.