Common as a noun-forming suffix for rooms or chambers of a particular kind. As a standalone everyday word for 'room', 部屋 is usually more natural; 室 is more formal or compound-like.
I reserved a meeting room from three in the afternoon.
This building has three laboratories.
wife of a high-ranking person
Rare historical or genealogical use for the wife of someone of high rank. It is not the normal modern word for 'wife'.
In genealogies, a lord's wife may be written as 室.
Rare use meaning a sword scabbard. In modern Japanese, 鞘 is the ordinary word for this meaning.
The use of 室 to refer to a sword scabbard is rare today.
Encampment mansion; Chinese constellation 室
Astronomical term for the Chinese 'Encampment' mansion, one of the twenty-eight lunar mansions and associated with 玄武.
室 is one of the twenty-eight lunar mansions and belongs to the Black Tortoise group.
guest room; cabin · drawing room; parlor
bedroom
Imperial Household; Imperial family
royal family; royal house
locked room; sealed room · secret room; hidden chamber
bathroom; bath
greenhouse; hothouse; conservatory
waiting room
one's own room
room temperature
hospital room; sickroom; ward
section chief; office head; room manager
Japanese-style room; washitsu
clubroom
entering a room · studying under a Buddhist teacher
one room; a single room
same room · sharing a room; occupying the same room
outside a room or building; outdoors
ventricle (of the heart)
tea room; tea ceremony room
exiting a room; leaving a room
waiting room; anteroom; green room
no vacancy; full occupancy
cabin; stateroom
living room; living space
Western-style room
concubine (of a noble)