windowpane; window glass
Refers to the glass pane(s) in a window. A common everyday noun.
The ball hit the windowpane and broke it.
窓ガラスが汚れているので拭いてください。
The window glass is dirty, so please wipe it.
double glazing; double-glazed window glass
Standard modern spelling using katakana for ガラス.
Ateji spelling using 硝子 for ガラス; rarely used today.
Compound of 窓 (まど, 'window') + ガラス ('glass'). ガラス is a loanword from Dutch 'glas'.