= hallo.

interjection, n alsohallo, hulloBrE[C]
[Date: 1800-1900; Origin: hollo a shout to call attention (16-19 centuries)]
used as a greeting when you see or meet someone
　Hello, John! How are you?
　Stanley, come and say hello to your nephew.
　Well, hello there ! I haven't seen you for ages.
used when answering the telephone or starting a telephone conversation
　Hello - may I speak to Anne?
used when calling to get someone's attention
　Hello! Is there anybody home?
used when you think someone is not acting sensibly or has said something stupid
　You didn't remember her birthday? Hello!
BrE used to show that you are surprised or confused by something
　Hello! What's happened here?
say hello
to have a quick conversation with someone
　Promise you'll look in and say hello when you have time.