interjection A greeting (salutation) said when meeting someone or acknowledging someone’s arrival or presence.
Hello, everyone.
interjection A greeting used when answering the telephone.
Hello? How may I help you?
interjection A call for response if it is not clear if anyone is present or listening, or if a telephone conversation may have been disconnected.
Hello? Is anyone there?
interjection Used sarcastically to imply that the person addressed has done something the speaker considers to be foolish, or missed something that should have been obvious.
You just tried to start your car with your cell phone. Hello?
interjection An expression of puzzlement or discovery.
Hello! What’s going on here?
noun "Hello!" or an equivalent greeting.
They gave each other a quick hello when they met, and went back on their merry ways.