Myalgia is the medical term for muscle pain. Muscle pain originates in any of the muscles in the body. Muscle pain may arise due to injury or overexertion, infections of the soft tissues, or inflammatory conditions. A number of conditions can be associated when generalized aches and pain, such as influenza, that are perceived to be muscle pain. Muscle pain can be localized to one muscle group or diffuse, involving multiple muscle groups. Muscle pain due to injury or overuse is most commonly localized to one area. Depending upon the cause, muscle pain can be mild or severe and debilitating. Muscle pain is the hallmark symptom of some chronic conditions like fibromyalgia. Related symptoms that can occur with muscle pain are tenderness, swelling, redness, or fever.

Melissa Conrad Stoppler, M.D., Muscle Pain (Myalgia): Symptoms and Signs, Medicine Net (updated Mar. 2, 2017), https://www.medicinenet.com/muscle_pain_myalgia/symptoms.htm