iPhone means iOS, so it's not only device, but also OS.
Only because it's a closed silo. If it were really your device then you could install whichever operating system you wanted.
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Actually by jailbreaking it's possible to run Linux on some iPhone models. https://www.xda-developers.com/apple-iphone-7-ubuntu-linux-checkra1n-project-sandcastle/
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Dont know @kristapsk iphone is a tangible thing but android no. ;)