What are organs called that serve no useful function in an organism?

Vestigial organs are remnants of structures that had important functions in the organism's ancestors but have lost most, if not all, of their original function through evolution. The term "vestigial" comes from the Latin word "vestigium," meaning a footprint or trace, reflecting the idea that these organs are traces of a past function. Common examples in humans include the appendix or the wisdom teeth.

In contrast, functional organs are those that still carry out essential processes in the body. Accessory organs typically refer to additional organs that assist in the functioning of a primary system, while non-essential organs may imply that an organism can survive without them but does not capture the historical context of these organs losing their function over time. Therefore, the correct designation for organs that no longer serve a useful function in an organism is vestigial organs.