A room number is a number assigned to a room within a

building A building, or edifice, is an enclosed structure with a roof and walls standing more or less permanently in one place, such as a house or factory (although there's also portable buildings). Buildings come in a variety of sizes, shapes, and func ...

. Its purpose is to identify a particular

room In a building or large vehicle, like a ship, a room is any enclosed space within a number of walls to which entry is possible only via a door or other dividing structure that connects it to either a passageway, another room, or the outdoors, that ...

, and help building inhabitants locate that room. Room numbers may consist of three digits, but can be any number of digits. The room number is generally assigned with the first digit indicating the

floor A floor is the bottom surface of a room or vehicle. Floors vary from simple dirt in a cave to many layered surfaces made with modern technology. Floors may be stone, wood, bamboo, metal or any other material that can support the expected load ...

on which the room is located.

Numbering systems

Similarly to how

house numbering House numbering is the system of giving a unique number to each building in a street or area, with the intention of making it easier to locate a particular building. The house number is often part of a postal address. The term describes the num ...

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.

Floor + One digit

Some places in

Brazil Brazil ( pt, Brasil; ), officially the Federative Republic of Brazil (Portuguese: ), is the largest country in both South America and Latin America. At and with over 217 million people, Brazil is the world's fifth-largest country by area ...

use a system in which the floor number is followed by only one number. In this system, apartment 52 is the second apartment on the 5th floor.

Floor + Two digits

In many places, the number of a room is determined by the number of the floor followed by two digits that inform the number of the room itself, even if there are less than 10 rooms per floor. This system is used in the

United States The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...

by the

University of Hawaiʻi at Mānoa The University of Hawaii at Mānoa (University of Hawaii—Mānoa, UH Mānoa, Hawai'i, or simply UH) is a public land-grant research university in Mānoa, a neighborhood in Honolulu, Hawaii. It is the flagship campus of the University of Haw ...

for buildings with less than 99 rooms per floor. This way, the 5th's floor 2nd apartment would be number 502. In

Sweden Sweden, formally the Kingdom of Sweden,The United Nations Group of Experts on Geographical Names states that the country's formal name is the Kingdom of SwedenUNGEGN World Geographical Names, Sweden./ref> is a Nordic countries, Nordic c ...

, floor numbers must have two digits, followed by two digits for the room number. Floor numbers start from 10 at ground level, and go down for underground floors, and up for above ground floors. In Sweden, the 5th's floor 2nd apartment would be number 1502.

Italy

Rome , established_title = Founded , established_date = 753 BC , founder = King Romulus ( legendary) , image_map = Map of comune of Rome (metropolitan city of Capital Rome, region Lazio, Italy).svg , map_caption ...

Italy Italy ( it, Italia ), officially the Italian Republic, ) or the Republic of Italy, is a country in Southern Europe. It is located in the middle of the Mediterranean Sea, and its territory largely coincides with the homonymous geographical ...

, 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.

References

building hotel terminology identifiers

number A number is a mathematical object used to count, measure, and label. The original examples are the natural numbers 1, 2, 3, 4, and so forth. Numbers can be represented in language with number words. More universally, individual number ...

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