This is the 3262nd most frequent Russian word.
окно
Window.
Here, 'окно' refers to a literal physical window in a building, commonly used in an everyday context.
Я открыл окно, чтобы проветрить комнату.
I opened the window to ventilate the room.
In this sentence, 'окно' metaphorically represents a time range or opportunity, showing idiomatic use in planning or scheduling.
Мы планируем отпуск, но окно для поездки пока не определено.
We are planning a vacation, but the window for the trip has not yet been determined.
Here, 'окно' is a colloquial term used in educational contexts to signify a gap in the schedule, like a break or a free period.