Pronunciation: [mˈʌli͡ən] (IPA) 
The word "mullion" is a term commonly used in architecture to refer to a vertical bar or division in a window. It is spelled as /ˈmʌliən/ according to the International Phonetic Alphabet. Here, the symbol /ʌ/ represents the "uh" sound, while /i/ represents the "ee" sound. The spelling of this word may be confusing due to its unusual combination of letters, but it can be easily remembered by breaking it down into syllables: mul-li-on.
A mullion is a structural element commonly found in windows or doors, which divides the opening into intervals or panels. It is a vertical or horizontal section made of various materials, such as wood, metal, or stone, that acts as a support or a framework for the glazing or fixed glass panes. Mullions are typically thicker and sturdier than the surrounding frame to provide additional strength and stability.
In the context of windows, mullions are especially significant in creating divided or multi-light windows, wherein smaller glass panes are separated by these sections, giving the appearance of multiple individual windows within a larger frame. This design choice is often seen in traditional or historical architecture, as it can enhance the aesthetic appeal of a building while maintaining structural integrity.
Beyond windows, mullions can also be found in other architectural elements, such as doors or screens, where they serve a similar purpose of dividing the overall space into distinct sections. Additionally, they can be decorative in nature, featuring intricate patterns or designs, particularly in ornate or historic buildings.
In summary, a mullion is a vertical or horizontal structural element that divides windows, doors, or other architectural features into separate panels. It provides support, stability, and visual appeal while accommodating glass panes or other materials.
• One of the upright bars which divide the several lights in a window-frame, being the stump of the division before it breaks off into the tracery of the window.
• To fit with mullions.
Etymological and pronouncing dictionary of the English language. By Stormonth, James, Phelp, P. H. Published 1874.
The word "mullion" is believed to have originated from the Middle French term "moillon", which meant a small piece of stone or wood. It is also related to the Old French word "moellon", which referred to a fragment of stone used in building. The Middle English version of the word was "moullon" or "moullon", pronounced as "mow-lyon". Over time, the pronunciation and spelling evolved, and it eventually became "mullion" as we know it today.
