"Hi" is an informal greeting that means hello [1][2][3][4]. It is commonly used in casual conversation and is generally suitable in everyday situations with people you know or in relaxed settings [1][2][3][4].

The word serves several primary functions: it is used as a greeting when meeting or addressing someone [1][2], and it functions as a friendly, casual alternative to the more formal "hello" [5][4]. In some contexts, "hi" can also be an abbreviation for other terms such as Hawaii or high intensity, though these uses are distinct from its primary greeting sense [1][2][6].

Both panel members confirmed the core definition and common usage patterns. One member offered to provide additional context by explaining differences between "hi," "hello," and "hey," which could be useful for learners seeking to understand nuances in informal English greetings.