Serratus posterior inferior is a muscle found in the back of the ribcage that helps in the process of breathing by contracting and relaxing, intercostal muscles. The muscle is also known by other synonyms, including the lower serratus muscle, serratus posterior inferior muscle, and serratus posterior inferior thoracic muscle. These synonyms are commonly used in anatomy and medical literature to refer to the same muscle. Other terms that can be used to refer to the serratus posterior inferior muscle include the subcostal muscle and the latissimus dorsi muscle. Knowing and understanding the different names for this muscle can aid in medical diagnoses and treatment options for patients experiencing back pain or respiratory issues.