An informal way to say hello. Used in casual situations with friends, family, and people you know.

Interjection. More casual and friendly than 'hello'. Used in conversation and writing (texts, emails to friends). Common extensions: 'Hi there!', 'Hi everyone!', 'Hi guys!' (informal address to a group).

In modern English, 'hi' has largely replaced 'hello' in informal speech, especially among younger people. 'Hi' is also common in casual written communication — texts, emails, and social media messages. In American English, 'Hey' is another very common casual greeting.