Have you ever wondered what the pieces of wood on the inside of a window that break it up into sections are called? Have you ever heard the term “window jamb” but didn’t actually know what it meant?

Windows have a surprising amount of terms that most regular people have probably never even heard of. In this blog, we would like to go over the basic terminology used to describe different parts of the window. Hopefully, this will be a helpful resource for anyone looking to get new windows. If you know what the different parts of the window are called, it will be easier for you to know what to ask for when you are ready to start window shopping.

If you’re in the market for a new window installation, call IBEX Window & Door. We can help you find quality windows that will fit your home perfectly.

An infographic showing the different terminology for window parts


The frame generally refers to the part of the window that holds everything in place. It is the part that sits inside the hole in the house siding. The frame has three sections, the head, the sill, and the jambs.

  • Head – The top section of the window frame
  • Sill – The bottom section of the window frame
  • Jamb – The side sections of the window frame

Sash or Panel

The sash or panel refers to the entire section of the window that contains the actual glass. In sliding windows, it would be the sections that slide side-to-side or up-and-down. In casement windows (the type of window pictured above), the sash or panel would refer to the section of the window that pivots away from the frame. Let’s explore the different parts of the sash/panel.

  • Rail – The horizontal beams on top and bottom of the sash/panel
  • Stile – The vertical beams on the sides of the sash/panel
  • Muntins – The decorative wood or vinyl on the inside of the sash/panel that breaks up the window into smaller panes
  • Panes – The sections of glass on the sash/panel windows can single panes or many panes broken up by muntins

    • Fun Fact: Double and triple pane windows actually have two or three layers of glass (respectively) and often the space between those layers is filled with argon or krypton gas! Click here to learn more!
  • Lock – the mechanical device that keeps the window from opening
  • Weather Stripping – Typically made from rubber, this lines the perimeter of the sash/panel to keep an airtight seal when the window is closed so that air does not sneak in from outside or vice versa


The trim refers to the parts surrounding the frame — typically made of wood or vinyl. The trim is important because no hole in the siding is ever a perfect fit so the trim covers any imperfections in the window fitting while improving the general aesthetic of the window — inside and out. Let’s explore the different pieces that make up the trim.

  • Casing or Trim Boards – Typically made from wood or vinyl, these boards surround the frame and cover any imperfections in the window fitting
  • Stool – This refers to the small shelf-like platform at the bottom of the window on the inside – many people commonly refer to this as the “sill” but they are actually mistaken
  • Apron – This is the decorative piece directly underneath the stool, often acting as a support for any weight that may be placed on the stool.

That covers the basics of window anatomy. We hope that now when you start shopping for your new windows, or when you are calling to have your window repaired, you will be better equipped to communicate exactly what you are looking for. If you have any other questions about window repair or window installation, call IBEX Window & Door today. We’d love to hear from you!