Mullion (noun)

A vertical structural element that divides a window or screen into smaller panes or sections.

Origin:

Derived from the latin "mullio" which means "thick post".

Examples:

1. The window had thin mullions that separated the panes.
2. The door had thick mullions that separated the panels.
3. The mullions on the windows were made of wood.
4. The mullions on the windows were painted white.
5. The mullions on the windows provided both structural support and aesthetic appeal.