いい; よい
いい; よい · ii; yoi · JLPT N5 · noun
good
👍 ii sounds like the letter E said twice: E-E for Excellent
いい (ii) is the everyday spoken form; よい (yoi) is the older, more formal one. Yoi still does the grammar work: the negative is よくない (yokunai) and the past is よかった (yokatta), never formed from ii.