Imperialism refers to the policy in which strong nations?

Imperialism refers to the policy in which strong nations extend their power over a territory either physically or by exercising strong economic and/or political influence and dominance over it.

The first manner described is related to the traditional conception of imperalism, as the one performed in America by the European powers in the 15th to 19th centuries. In turn, nowadays it is more common to use the term new imperialism which involves more subtler mechanisms of dominance which do not require to physically conquer any territory.