The pronunciation of "ni" in American English is typically a short, high-pitched vowel sound, similar to the "ee" in "see." This sound is produced by raising the tip of the tongue towards the roof of the mouth (the hard palate) while keeping the vocal cords tight. The mouth is kept open and the jaw is slightly relaxed. This pronunciation is consistent across various dialects in the United States, although there may be slight variations in tone and emphasis depending on the speaker's regional accent.

Data from the American English Pronunciation Dictionary by Ann Cook and Kenyon & Farquharson (2013) supports this description. The dictionary provides a detailed analysis of the phonetic transcription for "ni," which is represented as [ni]. This transcription aligns with the description of the vowel sound as a short, high-pitched "ee" sound. Additionally, the dictionary notes that the "ni" sound is often produced with a slight glottal stop at the end, which is a common feature in American English. This glottal stop is a brief closure of the vocal cords at the end of the vowel sound, contributing to the distinctive quality of the "ni" pronunciation in American English.