[tomesco]

The definition of organ in this article is closest to the body part definition. The use of organ here relies on a less common definition: roughly a constituent part of some larger whole that performs a specific function.

[shiroiushi]

Not just a specific function, but a necessary function. Usually, without an organ, the organism won't survive. So your fingers aren't organs, because you can survive (with some difficulty) without them, but without your stomach or heart or skin, you'll die.

[MBCook]

I think that’s a great summary.

As a native English speaker, it was understandable but feels rather foreign because you never hear parts of computers referred to that way these days.