private room; single room; room for one
A room for one person, often in a hotel, hospital, or dormitory; also a private room in a shared living space.
I booked a single room at the hotel.
The dormitory has private rooms and shared rooms.
private dining room; private room (restaurant)
A separate room in a restaurant, izakaya, or similar venue for a group to dine privately.
We reserved a private room at the traditional restaurant for the dinner meeting.
toilet stall; bathroom stall
An individual compartment in a public restroom.
All the toilet stalls were occupied.
I decided to stay in a private room at the hospital.
I reserved a private room for the birthday party.
I had a meal with a client in a private dining room.
I entered the toilet stall and locked the door.
小室 emphasizes the smallness of a space, whereas 個室 emphasizes that the room is private or for one person's exclusive use.
個室 specifically means a private, separate room, whereas 一室 simply means 'one room' without implying privacy.
個室 refers to a private room in a facility like a hospital or restaurant, whereas 自室 means a person's own personal room at home or in a dorm.
居室 refers to a living space shared or used for daily life, while 個室 means a private, individual room (e.g. in a hospital or hotel).
個室 (a private room) is a completely different word that happens to share the same pronunciation こしつ with 固執 (stubborn insistence).
密室 implies a room that is locked, sealed, or otherwise inaccessible from outside, whereas 個室 is just an ordinary private room (e.g. a hospital or hotel room) with no implication of being sealed off.
semi-private room; partially secluded space
Compound of 個 (ko, 'individual') and 室 (shitsu, 'room'). The kanji straightforwardly combine to mean 'individual room'.