What is the name of the last three or four vertebrae of the spine, commonly referred to as the tailbone?

The last three or four vertebrae of the spine, commonly known as the tailbone, are referred to as the coccyx. The coccyx is situated at the very end of the vertebral column and is composed of fused vertebrae, typically numbering between three to five. Its structure serves as an attachment point for various muscles, tendons, and ligaments, contributing to pelvic stability and support.

The sacrum, while part of the lower spine and positioned above the coccyx, comprises fused vertebrae that connect to the pelvis. The pelvis itself is a larger bony structure that includes the sacrum along with the hip bones, providing a substantial foundation for the spine and lower body. The lumbar region refers to the lower back consisting of five individual vertebrae and is located above the sacrum. However, it does not pertain to the tailbone structure at all. Thus, recognizing the coccyx as the tailbone is essential for understanding the anatomy and function of the lower vertebral column.