When does a meteor or meteorite grow in size to become an asteroid?
This is a semantics issue. A meteor is a lump of rock on collision course with something - they’re whizzing towards them. When they hit the ground they become a meteorite - a congealed lump of rock which has melted on the way through and landed on the ground. So a meteorite is something which has made it to a planet’s surface. An asteroid is a huge chunk of debris left in space which is effectively a failed planet that never managed to form.