What is the common name for the coccygeal bone?

The coccygeal bone is commonly referred to as the "tailbone." This term is derived from its small, triangular shape, which resembles the tail of an animal. The coccyx is the final segment of the vertebral column, and while it may not serve a significant functional purpose in modern humans, it does play a role in supporting the weight of the body when sitting and provides attachment for various muscles, tendons, and ligaments.

Understanding why it is labeled as the tailbone helps clarify its historical significance and anatomical positioning. The other choices, while related to the skeletal system, do not accurately identify the coccygeal bone. The pelvis and sacrum are larger structures composed of multiple bones, and "vertebrae" refers to the series of bones that make up the spine, none of which specify the coccyx alone. Therefore, "tailbone" is the correct common name for the coccygeal bone.