Brain-computer interface (BCI) is a technology that enables communication between the human brain and an external device, such as a computer or a prosthetic limb. Synonyms for BCI include neural interface, mind-machine interface, brain-machine interface, neuroprosthetics, and direct neural interface. Neural interface emphasizes the connection between the brain and external devices, while mind-machine interface highlights the interaction between the mind and technology. Brain-machine interface and direct neural interface refer to the direct communication between the brain and an external device. Neuroprosthetics refer to devices that replace or augment the function of a damaged or missing body part, while BCI technology includes broader applications, such as detecting emotions and thoughts.