The buttock bone is called the ischium (plural: ischia).
The ischium is one of the three bones that make up the pelvis. Specifically, it's the lower and back part of the hip bone that you sit on. Your "sit bones," technically known as the ischial tuberosities, are bony prominences of the ischia.
Here's a breakdown:
- Ischium: The actual name of the bone.
- Ischia: The plural form of ischium.
- Ischial tuberosities: The specific bony prominences on the ischium that bear your weight when you sit. These are often referred to colloquially as your "sit bones".
In summary, while people often refer to the "buttock bone," the correct anatomical term is the ischium, and the part you feel when sitting is the ischial tuberosity.
