^That's not entirely true; "hello there" is (and can be used as) a phrase without the rest. Besides greeting someone, hello there is a way to get someone's attention more strongly upon greeting, used to "signal" to someone to let them know they're the one being said 'Hello' to instead of someone else --in/near a crowd of people, for example. (It's easier to ignore a "hello" than a "hello there".)