Definition of HI in English:

HI

  • Hawaii (in official postal use).

Definition of hi in English:

hi

exclamation

informal
  • Used as a friendly greeting or to attract attention:

    ‘‘Hi there. How was the flight?’’
    • ‘‘Hi, is Danielle there?’ asked a guy's voice.’
    • ‘Hi there everyone. My name's Jeb.’
    • ‘Hi, Jessica, how are you?’
    • ‘I'd just like to say hi to my friends and family back home.’

Origin

Natural exclamation: first recorded in late Middle English.