Sternocleido Mastoideus, also known as SCM, is a muscle located in the neck that is responsible for turning and tilting the head. Although it is commonly referred to as SCM, there are several synonyms for this muscle depending on the context. Some of these synonyms include the sternomastoid muscle, the sternocleidomastoid muscle, the sternocleidomastoideus muscle, and the clavicle-cleidomastoid muscle. Each of these terms refers to the same muscle, describing its location and structure with minor differences in terminology. Regardless of which synonym is used, the SCM remains a crucial muscle for the function and movement of the neck and head.