[MereInterest]

Eh, different fields can have different definitions for the same word, and that's okay. If I tell a chemist that carbon is a metal, I would get a funny look. If I tell an astrophysicist that carbon is a metal, it is perfectly reasonable. Within the field of astronomy, metals are any element other than hydrogen and helium. There may be a similar difference in definitions here

[tricolon]

For those who are curious, you can read more here: https://en.wikipedia.org/wiki/Metallicity