Accessory attachable to camera body and having terminal layout

An accessory configured to be attached to a camera body, the camera body including a second camera-side clock terminal to which a second clock signal is input, a first camera-side power supply terminal that outputs first power, and a camera-side input terminal to which a signal indicating whether or not data communication is allowed is input, the accessory comprising:

• a second terminal that is brought into contact with the first camera-side power supply terminal;
• a sixth terminal that is brought into contact with the camera-side input terminal;
• a tenth terminal that is brought into contact with the second camera-side clock terminal to output the second clock signal from the tenth terminal to the camera body;
• a first terminal group comprising a plurality of terminals between the second terminal and the sixth terminal;
• and
• a second terminal group comprising a plurality of terminals between the sixth terminal and the tenth terminal, wherein
• a number of terminals in the first terminal group is same as a number of terminals in the second terminal group.