pane
n.a single sheet of glass in a window or door. You use this word when talking about one piece of glass rather than the whole window frame.
n.a single sheet of glass within a window, door, or screen. In computing, refers to a distinct section of a window or interface that displays specific information.
“A bird flew right into the window pane.”
“The storm was so strong that it cracked a pane of glass in the kitchen window.”
“The architect chose to use a single large pane for the storefront to maximize the natural light entering the gallery space during the winter months.”
Often used in the phrase 'a pane of glass'.
“One of the windows was missing a glass pane.”
From Middle English pane, pan, from Old French pan, from Latin pannus, from Proto-Indo-European *peh₂n- (“fabric”). Doublet of pagne, pan, and pannus.
Etymology adapted from Wiktionary, available under CC BY-SA 4.0.