Room number

[2][3] Similarly to how house numbering systems vary depending on the region, room numbering systems do too.

Some numbering systems inform the floor in which the room is located, but not all.

This system is used in the United States by the University of Hawaiʻi at Mānoa for buildings with fewer than 99 rooms per floor.

In Rome, Italy, some addresses explicitly mention which floor ("piano") the apartment is located at.

So an address could read "piano 5, interno 2" for the second apartment in the 5th floor.