The moon has a name. It called...
Duh Duh Duh...
The moon.
It's not just 'a' moon, it's 'the' moon, because it's our moon so why would we need to call it anything else.
Referring to the moon by 'the moon' is perfectly acceptable and pretty much everyone knows what you mean.
When talking to someone about a different moon, you either refer to it using the name of the planet it's orbiting or the given scientific name, so everyone will still know what you're talking about (well, if they know about the moons in the system anyway)
Duh Duh Duh...
The moon.
It's not just 'a' moon, it's 'the' moon, because it's our moon so why would we need to call it anything else.
Referring to the moon by 'the moon' is perfectly acceptable and pretty much everyone knows what you mean.
When talking to someone about a different moon, you either refer to it using the name of the planet it's orbiting or the given scientific name, so everyone will still know what you're talking about (well, if they know about the moons in the system anyway)