Private Room
One's Own Room
noun
An individual room just for you is your own private room. How nice!
こしつ
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
小さい子がいると個室い酒屋の存在はありがたいです。
When you have small kids, the existence of izakaya with private rooms is appreciated.
コウイチはシェアハウスで自分の個室がないという生活をもう五年も続けている。
Koichi's been living in a shared house without his own room for more than five years now.
忘年会に個室を予約しました。
I reserved a private room for our year-end party.