organ
1.
2. Biology. A differentiated part of an organism, such as an eye, a wing, or a leaf, that performs a specific function.
3. An instrument or agency dedicated to the performance of specified functions: The FBI is an organ of the Justice Department.
4. An instrument or a means of communication, especially a periodical issued by a political party, business firm, or other group.
[Middle English, from Old French organe and from Old English organe, both from Latin organum, tool, instrument, from Greek organon.]