Vitre vs. carreau
In French, both vitre and carreau can translate to window pane in English, but they are not interchangeable. The choice between them depends on whether you are referring to the glass material as a whole or to a smaller, individual section of a divided window.
Vitre
A2The word vitre refers to the pane of glass itself—the material. It's the general term used for a sheet of glass in a window, a door, a picture frame, or a vehicle. It is most often used for large, single panes of glass.
Le chat adore s'asseoir derrière la vitre pour regarder les oiseaux.
(The cat loves to sit behind the glass to watch the birds.)
J'ai nettoyé toutes les vitres de la maison ce week-end.
(I cleaned all the windows of the house this weekend.)
Peux-tu ouvrir la vitre de la voiture ? Il fait chaud.
(Can you open the car window? It's hot.)
Le vent a fait vibrer la grande vitre du salon.
(The wind made the large living room window pane vibrate.)
Il faut remplacer la vitre de cette porte-fenêtre car elle est fissurée.
(We need to replace the glass of this French door because it is cracked.)
Carreau
B1The word carreau refers to a single, smaller pane of glass that is part of a larger window divided into sections by glazing bars (mullions). It highlights one square or rectangular unit within a grid. Note that carreau also commonly means tile or a check/plaid pattern.
Un seul carreau de la vieille fenêtre est cassé, les autres sont intacts.
(Only one pane of the old window is broken, the others are intact.)
Cette porte ancienne est composée de six petits carreaux de verre.
(This old door is made of six small glass panes.)
Le vitrier est venu pour changer le carreau que j'avais brisé.
(The glazier came to change the pane I had broken.)
J'ai choisi un carrelage avec des carreaux bleus pour la salle de bain.
(I chose a tiling with blue tiles for the bathroom.)
Il portait une chemise à carreaux rouges et noirs.
(He was wearing a red and black checkered shirt.)
Summary
To summarize, use vitre when talking about the glass sheet in general, a large single pane of glass, or a car window. Use carreau when referring to one of the smaller, individual panes in a window that is divided into multiple sections. Think of vitre as the material and carreau as a distinct, often square, unit within a larger structure.