Spa and Shower room

Spa noun - A building or room used for sports activities and exercising.

Shower room and spa are semantically related in place topic. In some cases you can use "Shower room" instead a noun "Spa", when it comes to topics like bath, bathroom.

Shower room noun - A room with several showers.

Spa and shower room are semantically related in place topic. You can use "Spa" instead a noun phrase "Shower room", if it concerns topics such as bath, bathroom, room for bathing, toilet use.