The arm bones, also known as the upper limb bones, are composed of the radius, humerus, ULNA, and their plural forms. The radius is an 8-letter bone located on the thumb side of the forearm and is connected to the humerus, which is a 6-letter bone located in the upper arm. The ULNA is a 4-letter bone located on the little finger side of the forearm and is connected to the humerus. Its plural form, ulnae, is a 5-letter word. The plural form of the radius, RADII, is also a 5-letter word. Together, these bones form the skeletal structure of the arm and allow for movement and flexibility.