kabineto

Two senses, and they are the same word for a good reason. The first is physical: a small room set aside for concentrated work - a study, a private office, a doctor's consulting room. The Reta Vortaro's definition is exactly that, "a room intended for mental work". The second is political: the ministers who form a government's inner circle, so la brita kabineto is the British cabinet. The second grew out of the first, because that inner circle originally met in the monarch's private room, and English did the identical thing with the identical word.

What it is not is a piece of furniture. This is the fence English speakers need. A kitchen cabinet, a display cabinet, a filing cabinet: all of those are ŝranko in Esperanto, and kabineto for any of them will simply be misread. If in doubt, ask whether you can walk into it.

How it sits against its neighbours. An oficejo is an office in the general sense - ofic- plus the place suffix -ej- - and may hold forty people. A kabineto is private and usually one person's. A ĉambro is any room at all. On the political side, the registaro is the government as a whole, the kabineto is its senior ministers, and the ĉefministro chairs it.