google-fonts/cc-by-sa/knowledge/glossary/terms/fill_axis/term.textproto

name: "Fill axis (FILL)"
excerpt: "An axis found in some variable fonts, intended to provide a treatment of the design that fills in transparent forms with opaque ones."
related_lessons: "introducing_variable_fonts"
related_lessons: "designing_with_variable_fonts_in_desktop_apps"
related_lessons: "styling_type_on_the_web_with_variable_fonts"