hi

The word 'hi' is a modern, informal variant of the Middle English interjection 'hey', which was used as a call to attract attention or express surprise. 'Hey' itself is of imitative origin, a natural exclamation found in various forms across many languages, likely stemming from a Proto-Indo-European base like kī- or kei-, used to call or command. Its journey into a standard greeting in American English during the 19th century illustrates how a simple, spontaneous sound can become lexicalized and standardized within a language's social conventions, shedding its original imperative force to become a neutral, friendly salutation.

This is a simplex word, a natural exclamation. It is a variant of the earlier greeting 'hey', which itself is a natural call to attract attention, found in many languages.