“If it is in a stable orbit around Earth, then it is a moon.”
Some light reading ...
https://en.wikipedia.org/wiki/Co-orbital_configuration
If an object or craft were to enter our solar system with intention of being in proximity to Earth, would it not be more practicable to enter into this kind of “joint” orbit with Earth around the sun, rather than try to actually go into orbit around Earth.
I would think it would save a lot of fuel.
I read the first three lines and realized that I had written this article for Wiki during my REM stage of sleep a few years ago! Mmmmaybe not?