This is the 13th most frequent Japanese word.
い
The Japanese "い" (i) is a hiragana character, representing the vowel sound "i" or the concept of "stomach" (胃) in kanji.
The word "い" is part of the adjective "いい" (meaning 'good' or 'nice').
いい天気ですね。
It's nice weather, isn't it?
The sequence "い" appears in "意志" (will), where "意" contributes to the compound meaning as 'mind' or 'intent.'
勝つ意志を掲げる。
Raise the will to win.
The "い" here is part of the combination "います" (to exist, used for animate entities).