Which type of fracture is referred to as a greenstick fracture?

A greenstick fracture is classified as an incomplete fracture. This term is used to describe a type of fracture that occurs typically in children, where the bone does not break all the way through but is instead partially broken, similar to how a green twig bends and partially breaks when force is applied. The bone bends but does not result in a complete separation, hence the description of it being "incomplete."

In the context of the other options, a complete fracture refers to a fracture that completely breaks the bone across its width. A pathological fracture occurs due to an underlying disease that weakens the bone, such as osteoporosis or cancer. Hairline fractures, also known as stress fractures, are very fine cracks in the bone that can develop from repetitive stress or overuse rather than a single injury. Understanding the characteristics of these different types of fractures helps in effective diagnosis and appropriate treatment of skeletal injuries.