> semitones? a fifth? a fifth of what? it is seven notes or 3/2's there is no 5.

I learned to read sheet music as a kid by my mom taking me to piano lessons. I cannot play the piano but I know where the notes are that correspond to the sheet music. I parlayed that into learning to play woodwinds when I got older. Even that was just enough to have fun. Nothing about it was me being serious about being a musician. So when other students would talk about 5ths and 3rds, I was totally lost. Then someone just said transpose the note up/down 5 notes (or 3 or whatever). They said it confidently, and they were first chair, so I went with it. I've never needed to know it, as I just play the notes as written on the sheet. I've never gigged where I had to play different keys.

But yeah, the fifth nomenclature confused the hell out of me too