～室
～しつ · ～shitsu · JLPT N2 · noun
room
🚪 室 = 宀 roof + 至 arrive: the place you reach under a roof, a room
室 (shitsu) appears in room words like 教室 classroom and 会議室 meeting room. As a suffix it numbers or labels rooms, e.g. 三室 for three rooms. Sound hook: shitsu sounds like she sits, and she sits in a room.
室 — roof 宀 + arrive 至
A semantic compound: 宀 (roof/house) over 至 (to arrive). The image is a place one arrives at and stays in — an inner room. From 'inner chamber' the meaning broadened to 'room' generally, and by extension to specialized rooms like an office or laboratory.