In music, mi is a singing-name for a note. When you climb the scale as do, re, mi, fa, so, la, ti, do, mi is the third step. Teachers like these little names because you can sing a tune without stopping to say letter-names like C or E. Though actually, countries do not all mean the same pitch by mi. In a “movable do” class, mi is simply the third step of whatever scale you are in. In a “fixed do” class — the kind many music students in Taiwan meet — do is always C, and mi is always the note E. Same word, two maps. The name is very old. Singing teachers once used a Latin hymn to remember the scale; mi was cut from mira, a word in that hymn meaning wonders or miracles. It is a classroom and choir word, not a fancy one.