The term imperialism was a new word in the mid-19th century.
According to the Oxford English Dictionary (OED), it was first
recorded in 1858, to describe Pax Britannica. At this time,
imperialism was regarded as a new phenomenon deserving of a new
word to describe it. Moreover, according to the OED, in 19th
Century England, imperialism, was generally used only to
describe English policies. However, soon after the invention of
the term, imperialism was used in reference to policies of the
Roman Empire. In the 20th century, the term has been used to
describe the policies of both the Soviet Union and the United
States although analytically these differed greatly from each
other and from 19th-century imperialism. Furthermore, the term
has been expanded to apply, in general, to any historical
instance of the aggrandizement of a greater power at the expense
of a lesser power. Consequently, historians today refer to
European imperialism following the Franco-Prussian War as the
new imperialism. Between 1871 and 1914,