mul·lion /ˈmʌljən/
豎框,直欞,放射狀框
Mul·lion n. Arch. (a) A slender bar or pier which forms the division between the lights of windows, screens, etc. (b) An upright member of a framing. See Stile.
Mul·lion, v. t. To furnish with mullions; to divide by mullions.
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mullion
n : a nonstructural vertical strip between the casements or
panes of a window (or the panels of a screen)