Rus vs. Russia: What's the Difference?

Rus and Russia Definitions
Rus
The medieval Russian state established by Scandanavian traders in the 9th century; the capital was first in Novgorod and then in Kiev
Russia
A country of Europe and Asia.
Russia
A former communist country in eastern Europe and northern Asia; established in 1922; included Russia and 14 other soviet socialist republics (Ukraine and Byelorussia an others); officially dissolved 31 December 1991
Russia
Formerly the largest Soviet Socialist Republic in the USSR occupying eastern Europe and northern Asia
Russia
A former empire in eastern Europe and northern Asia created in the 14th century with Moscow as the capital; powerful in 17-18th centuries under Peter the Great and Catherine the Great when Saint Petersburg was the capital; overthrown by revolution in 1917
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Russia
A federation in northeastern Europe and northern Asia; formerly Soviet Russia; since 1991 an independent state