Myalgia means symptoms of pain in the muscles.
Polyarthritis means inflammation in the many joints - by definition 4 or more. Oligoarthritis means inflammation in few joints - by definition 3 or less. Monoarthritis means inflammation in one joint. Bursitis is inflammation of the bursae - sacs of fluid that lie adjacent to certain tendons insertion's into bone. Enthesitis means inflammation at the site of tendon insertion into bone.