Wow that's a weird exception; https://en.wikipedia.org/wiki/Litre https://en.wikipedia.org/wiki/Litre I was always tought that the liter was an SI unit, I mean

Wow that's a weird exception; https://en.wikipedia.org/wiki/Litre https://en.wikipedia.org/wiki/Litre I was always tought that the liter was an SI unit, I mean, it's defined in terms of SI units, I know it's not a base unit, but weird that it's singled out as "well, you're technically SI compatible, and you're defined in SI units, but we're not gonna let you be part of the group" :) It even has an official SI symbol (L), despite not being an SI unit, what?!