Mullion
/ˈmʌl.jən/noun
A vertical bar between the panes of a window or between the lights of an arcade.
Did you know?Mullion comes through Old French from Medieval Latin *mullio*, a word tied to the architectural “middle” of an opening, showing how builders turned structure itself into a language of light.
Etymological Timeline
Medieval Latin
ML
mullio
“A central upright division in an opening or window”
Old French
OF
mullion
“A vertical division in a window or opening”
14th Century
English
mullion
“A vertical bar dividing a window into lights”
Modern English
English
mullion
“A vertical bar between panes of glass or within an arcade”