What is the Greek word for instrument?

There isn't one single perfect Greek word for "instrument" as the meaning depends on the context. However, several words could be used depending on what kind of instrument is meant:

* ὄργανον (organon): This is the most common and broadly applicable word. It can refer to a musical instrument, a tool, or even an organ of the body. This is probably the closest single equivalent.

* More specific words would be needed for particular types of instruments. For example, a musical instrument might be κίθαρις (kitharis) (lyre), αὐλός (aulos) (aulos - a type of double pipe), etc. For tools, you'd need a word specific to the tool's function.