In general, we use northern, southern, eastern, and western to talk about more general, indefinite areas - and north, south, east, and west in official names of places:
fficial names of places:
North America
South Africa
East Timor
West Virginia
General areas:
northern England
southern India
eastern Australia
western Europe
the northern border of the country
the southern side of the house
the eastern coastline
(although in the U.S. we say "east coast" and "west coast")
the western part of the state
ne exception - an example of an "official name" that uses northern and southern -is saying the Northern/Southern Hemisphere to refer to the two halves of the earth divided by the equator.