or·gan·elle 
(ôr′gə-nĕl)
(ôr′gə-nĕl)n.
A differentiated structure within a cell, such as a mitochondrion, vacuole, or chloroplast, that performs a specific function.
[New Latin organella, diminutive of Medieval Latin organum, organ of the body, from Latin, implement, tool; see ORGAN.]