Many anatomical terms descriptive of bone are defined in anatomical terminology, and are often derived from Greek and Latin.
A long bone is one that is cylindrical in shape, being longer than it is wide. However, the term describes the shape of a bone, not its size, which is relative. Long bones are found in the arms (humerus, ulna, radius) and legs (femur, tibia, fibula), as well as in the fingers (metacarpals, phalanges) and toes (metatarsals, phalanges). Long bones function as levers; they move when muscles contract. They are responsible for the body's height.
A short bone is one that is cube-like in shape, being approximately equal in length, width, and thickness. The only short bones in the human skeleton are in the carpals of the wrists and the tarsals of the ankles. Short bones provide stability and support as well as some limited motion.
The term "flat bone" is something of a misnomer because, although a flat bone is typically thin, it is also often curved. Examples include the cranial (skull) bones, the scapulae (shoulder blades), the sternum (breastbone), and the ribs. Flat bones serve as points of attachment for muscles and often protect internal organs. Flat bones do not have a medullary cavity because they are thin.
An irregular bone is one that does not have an easily classified shape and defies description. These bones tend to have more complex shapes, like the vertebrae that support the spinal cord and protect it from compressive forces. Many facial bones, particularly the ones containing sinuses, are classified as irregular bones.
A sesamoid bone is a small, round bone that, as the name suggests, is shaped like a sesame seed. These bones form in tendons (the sheaths of tissue that connect bones to muscles) where a great deal of pressure is generated in a joint. The sesamoid bones protect tendons by helping them overcome compressive forces. Sesamoid bones vary in number and placement from person to person but are typically found in tendons associated with the feet, hands, and knees. The only type of sesamoid bone that is common to everybody is the kneecap (patella, pl. patellae) which is also the largest of the sesamoid bones.
A condyle is the round prominence at the end of a bone, most often part of a joint - an articulation with another bone. The epicondyle refers to a projection near a condyle, particularly the medial epicondyle of the humerus. These terms derive from Greek. [a]
A ramus (Latin: branch) refers to an extension of bone, such as the ramus of the mandible in the jaw or Superior pubic ramus. Ramus may also be used to refer to nerves, such as the ramus communicans.
A line refers to a long, thin projection, often with a rough surface.
A spine, as well as referring to the spinal cord, may be used to describe a relatively long, thin projection or bump.
These terms are used to describe bony protuberances in specific parts of the body.
The Malleolus (Latin: "small hammer") is the bony prominence on each side of the ankle.  These are known as the medial and lateral malleolus. Each leg is supported by two bones, the tibia on the inner side (medial) of the leg and the fibula on the outer side (lateral) of the leg. The medial malleolus is the prominence on the inner side of the ankle, formed by the lower end of the tibia. The lateral malleolus is the prominence on the outer side of the ankle, formed by the lower end of the fibula.
The following terms are used to describe cavities that connect to other areas:
A foramen is any opening, particularly referring to those in bone.  Foramina inside the body of humans and other animals typically allow muscles, nerves, arteries, veins, or other structures to connect one part of the body with another.
A canal is a long, tunnel-like foramen, usually a passage for notable nerves or blood vessels.
The following terms are used to describe cavities that do not connect to other areas:
The following terms are used to describe the walls of a cavity:
Bones are commonly described with the terms head, neck, shaft, body and base
The head of a bone usually refers to the distal end of the bone. The shaft refers to the elongated sections of long bone, and the neck the segment between the head and shaft (or body). The end of the long bone opposite to the head is known as the base.
|Bone feature||Definition||Etymologic memory aid|
|apophysis||Any of various processes or protuberances on a bone.||apo- + physis, "outward from the growth part; outgrowth"|
|diaphysis||The long, relatively straight main body of a long bone; region of primary ossification. Also known as the shaft.||dia- + physis, "between the growth parts"|
|epiphysis||The end regions of a long bone; regions of secondary ossification.||epi- + physis, "on top of the growth part"|
|physis (epiphyseal plate)||Also known as the growth plate. In a long bone it is a thin disc of hyaline cartilage that is positioned transversely between the epiphysis and metaphysis. In the long bones of humans, the epiphyseal plate disappears by twenty years of age.||physis, "the growth part"|
|metaphysis||The region of a long bone lying between the epiphysis and diaphysis.||meta- + physis, "the transitional part (between shaft and end) containing the growth part"|
The cortex of a bone is used to refer to its outer layers, and medulla used to refer to the inner surface of the bone. Red marrow, in which blood is formed is present in spongy bone as well as in the medullary cavity, while the fatty yellow marrow is present primarily in the medullary cavity.