The tailbone is the small, triangular bone at the very bottom of your spine. Its scientific name is the coccyx. When you sit down, you can feel your tailbone pressing against your chair, right between where your legs meet your back.

Your spine is made up of many small bones stacked like blocks, starting at your skull and running all the way down your back. The tailbone is the final piece, made of three to five tiny bones fused together. It's called the tailbone because scientists believe it's what remains of the tail our ancient ancestors had millions of years ago, before humans evolved to walk upright.

Even though it's small, your tailbone serves important purposes. Muscles and ligaments connect to it, helping support your pelvic floor and making it possible to sit comfortably. When someone falls directly on their bottom or gets hit there during sports, they might bruise or even break their tailbone, which can make sitting painful for weeks.

People sometimes call it their “tailbone” in everyday conversation, while doctors use the more formal term “coccyx.” Either way, it's the same bone: that little point at the base of your spine that reminds us of our evolutionary past.