Bounding Box

A bounding box (usually shortened to bbox) is an area defined by two longitudes and two latitudes, where:

They usually follow the standard format of:

bbox = left,bottom,right,top
bbox = min Longitude , min Latitude , max Longitude , max Latitude

For example, Greater London is enclosed by:

{{bbox|-0.489|51.28|0.236|51.686}}
(bbox=-0.489,51.28,0.236,51.686)

The "export data" link on the main website allows you to draw a box, and the coordinates of the edges are shown to you.

In a WikiProject having a params sub-page, you can get the bounding box by using the template pBbox.

Nominatim API

Nominatim API returns a boundingbox property of the form:

 south Latitude, north Latitude, west Longitude, east Longitude

For example, Greater London in JSON format:

 "boundingbox":["51.2867602","51.6918741","-0.5103751","0.3340155"]

Boundingbox can be used to graphically define a BBOX and cut&paste the coordinates in various formats.

The OSM.org map has a feature to define a BBOX (using "manually select a different area"), which can then be used to export map data.

The order of values in the bounding box used by Overpass API is (South, West, North, East):

minimum latitude, minimum longitude, maximum latitude, maximum longitude

See more details in the Overpass API Wiki.