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win·dow (wĭndō)
a. An opening constructed in a wall, door, or roof that functions to admit light or air to an enclosure and is often framed and spanned with glass mounted to permit opening and closing.
b. A framework enclosing a pane of glass for such an opening; a sash.
c. A pane of glass or similar material enclosed in such a framework: The ball broke the window.
a. An opening or transparent part that resembles a window in function or appearance: a sail window.
b. The transparent panel on a window envelope.
3. The area or space immediately behind a window, especially at the front of a shop: goods displayed in the window.
4. A means of access or observation: St. Petersburg was Peter the Great's window onto the Baltic.
5. An interval of time during which an activity can or must take place: a window of opportunity for a space mission; a window of vulnerability when the air force was subject to attack.
6. Strips of foil dropped from an aircraft to confuse enemy radar; chaff.
7. A range of electromagnetic frequencies that pass unobstructed through a planetary atmosphere.
8. Computers A rectangular area on a screen in which a document, database, or application can be viewed independently of the other such areas.
9. Aerospace
a. A launch window.
b. An area at the outer limits of the earth's atmosphere through which a spacecraft must pass in order to return safely.

[Middle English, from Old Norse vindauga : vindr, air, wind; see wē- in the Appendix of Indo-European roots + auga, eye; see okw- in the Appendix of Indo-European roots.]

Word History: The source of our word window is a vivid metaphor. Window comes to us from the Scandinavian invaders and settlers of England in the early Middle Ages. Although we have no record of the exact word they gave us, it was related to Old Norse vindauga, "window," a compound made up of vindr, "wind," and auga, "eye," reflecting the fact that at one time windows contained no glass. The metaphor "wind eye" is of a type beloved by Norse and Old English poets and is called a kenning; other examples include Old Norse gjālfr-marr, "sea-steed," for "ship" and Old English hron-rād, &;ldquo;whale-road," for "sea."

The American Heritage® Dictionary of the English Language, Fifth Edition copyright ©2022 by HarperCollins Publishers. All rights reserved.

Indo-European & Semitic Roots Appendices

    Thousands of entries in the dictionary include etymologies that trace their origins back to reconstructed proto-languages. You can obtain more information about these forms in our online appendices:

    Indo-European Roots

    Semitic Roots

    The Indo-European appendix covers nearly half of the Indo-European roots that have left their mark on English words. A more complete treatment of Indo-European roots and the English words derived from them is available in our Dictionary of Indo-European Roots.