When it comes to home improvement, most homeowners know the big stuff: paint colors, flooring options, and furniture styles. But when the topic shifts to window supplies, the vocabulary can suddenly feel like a foreign language. Whether you’re planning a window upgrade, shopping for replacements, or simply trying to understand your contractor, knowing the correct terms can save time, money, and miscommunication.
In this glossary, we break down 25 essential terms every homeowner should understand—because making smart decisions starts with speaking the language.
1. Window Frame
The rigid structure that surrounds and supports the entire window system, typically made of wood, vinyl, aluminum, or fiberglass.
2. Sash
The part of the window that holds the glass panes and moves when you open or close the window. In double-hung windows, there are usually two sashes.
3. Glazing
Refers to the glass within the window. Single, double, or triple glazing indicates how many layers of glass are present.
4. Low-E Glass
Short for “low emissivity,” this type of glass has a thin coating that reflects heat, improving energy efficiency.
5. Window Pane
A single sheet of glass. Multiple panes can be used in one window for added insulation.
6. Mullion
A vertical or horizontal bar that separates and supports individual panes of glass within a window or between multiple windows.
7. Muntins
These are the grid-like bars that divide a single window sash into smaller panes for aesthetic purposes. They don’t necessarily affect function.
8. Casement Window
A window type that is attached to its frame by one or more hinges and opens outward like a door.
9. Awning Window
Hinged at the top and opening outward from the bottom, ideal for letting in air while keeping rain out.
10. Double-Hung Window
A classic window design where both the upper and lower sashes can slide vertically to open.
11. Single-Hung Window
Only the bottom sash moves vertically; the top one remains fixed.
12. Bay Window
A combination of three windows that project outward from the wall, creating a nook and allowing more light.
13. Bow Window
Similar to bay windows but with more panes and a more rounded, curved appearance.
14. Window Apron
The decorative trim piece is beneath the window sill on the interior wall.
15. Sill
The horizontal piece is at the bottom of the window frame. It can be functional (to channel water away) or purely decorative.
16. Jamb
The vertical sides of the window frame support the sashes.
17. Head
The top horizontal part of the window frame.
18. Weatherstripping
Material used to seal gaps around the window sash to prevent air and water infiltration.
19. Argon Gas
An inert gas used between window panes in double- or triple-glazed windows to improve insulation.
20. Cladding
A protective layer (often aluminum or vinyl) is applied to the outside of a wood window frame to reduce maintenance.
21. Egress Window
A window large enough to allow escape in case of an emergency—commonly required in bedrooms or basements.
22. Window Flashing
A thin material used to prevent water from entering the structure at window openings.
23. Window Film
A thin laminate that can be applied to glass for UV protection, privacy, or safety.
24. Transom
A smaller window placed above a door or larger window, often used for natural light or ventilation.
25. Grilles
Decorative elements create the appearance of divided panes in a window without actually separating the glass.
Choosing the Right Window Supplies Matters
Understanding this vocabulary isn’t just for show—it directly impacts how effectively you communicate with installers, designers, and sales reps. If you’re browsing home improvement stores or consulting a contractor, confidently using terms like “Low-E glazing,” “muntins,” or “weatherstripping” can help ensure you’re getting what you need.
Integrating door and window supplies cohesively can make a big difference in aesthetics and energy efficiency when exploring broader home renovations. Matching hardware, complementary designs, and compatible energy ratings ensure a unified and high-performing outcome for your entire home.
Conclusion
A strong grasp of these 25 window-related terms empowers homeowners to make informed decisions, avoid costly mistakes, and engage in meaningful dialogue with professionals. Whether renovating an old house, building a new one, or simply replacing a few windows, these terms provide the foundation for smarter choices.
